Change Log:
- August 25th 2022 - Initial version published on r/RepTime
- March 9th 2023 - Updated version published on RWI. Updated to include information about the new SH3285 found in C+ Factory GMTs and DD3285 found in Clean Factory GMTs.
- March 14th 2023 - Update to include a link to Steve's amazing 3135 photographic comparison, and to correct images in the 3135 section. And to add a collage of the different 318X GMT movements (thank you @KJ2020 for this). And added a reference to @CTime photo comparison thread between gen and Dandong 4130 movements.
- March 15th 2023 - Added link to CTime's macro picture part by part comparison of vr3186 to gen.
- June 28th 2023 - Updated to include the new Shanghai 4130 Daytona movement, and to include some additional reliability information about the Shanghai 3285 GMT movement.
- July 26th 2023 - Fixed broken images. No information updates.
- September 24th 2023 - Added a section about the new VR3255 DayDate clone movement. And Added a section about the naming conventions of rep rolex movements.
- December 28th 2023 - Added info about the mod that converts a VS3235 into a 3230 movement (i.e. the phantom date fix mod).
- January 12th 2024 - Added information about the new "4131" Daytona movement from AR+F, and the skeletonized 4130 movement from SONIC Factory.
- January 15th 2024 - Corrected some information about the new
Dandong Shanghai 4131 movement used in the AR+F 126500 Daytonas.
Guide
When buying a high end replica watch, it’s important to consider both what’s on the outside and what’s on the inside. The factories in China have invested millions of dollars in re-producing exact copies of various Swiss watch movements. The accuracy of the replication varies, as does their reliability of these movements. In this guide I hope to be able to give you a basic understanding of which mechanical movements are good, which ones are ok, and which ones to avoid, and importantly, how to tell the various movements apart, since the information listed on Trusted Dealer (TD) websites in the descriptions isn’t terribly accurate.
Naming Conventions
Watch movements are often labeled with one or two letters followed by the Rolex movement number that they're a clone of. For example, the VS3235 is a clone of the Rolex 3235 movement. The prefix letters are important, but aren't assigned based on any consistent principals. Sometimes the letters are applied based on which watch factory exclusively uses the movement (e.g. VSF is the exclusive user of VS3235 movements, so that's where the "VS" part of the movement name comes from). But this pattern isn't universal, currently Clean Factory is the exclusive user of the new DD3285 movement, but that movement gets its DD prefix from "Dandong movement factory", the maker of the movement. In theory it would be best to use the movement factory names as the prefixes since movements like the VR3235 get the "VR" from the fact that they were initially used by the watch factory VRF, but are now used by many factories, so the VR3235 would be better named the SH3235 since it is made by the Shanghai movement factory. However, there are in fact two movement factories in Shanghai. Further complicating naming conventions is the fact that sometimes the letters "A" or "SA" are used as prefixes to simply mean "Asian" or "Super Asian". In conclusion:
- Rep movement naming conventions are a mess.
- Don't trust what is written on TD websites.
- Learn to identify movements based on the descriptions and labeled images below.
40mm Submariner (1166XX and 114060)
For 40mm submariners (i.e. those with reference number 1166XX), there are six options in order of quality:
- VS3135 (date version), VS3130 (no-date version)
- VR3135 (date version), VR3130 (no-date version)
- SH3135 (date version), SH3130 / AR3130 (no-date version)
- SA3135 (date version), SA3130 (non-date version)
- A2824
- A2836
Genuine Rolex Caliber 3135
For reference here’s the genuine Rolex caliber 3135. Note how there is only one arm (the beat adjustor -- red arrow) on the balance bridge of the genuine movement. This is because the genuine movement has a “free sprung” balance. That means on the genuine movement the speed of the movement is regulated (i.e. adjusting how fast or slow the movement runs) by adjusting the moment of inertia of the balance wheel via tiny weighted screws on the rim of the wheel (green arrows). On all replica movements, regulation is done via a regulation arm that can be adjusted to lengthen or shorten the effective length of the hairspring. That’s why you see only one arm on the genuine movement, but two arms on the replica movements. Also note that the 3135 movement's rotor does NOT run on ball bearings (blue arrow).
VS3135 & VS3130
This is an excellent movement. The part finishing quality and engraving is good. The hairspring mounted clockwise. This is the best clone of the Rolex 3135 movement. Note, there is a VS3130 version of this movement which is used on the no-date 40mm VSF subs (ref number 114060). The VS3130 is of equal quality to the VS3135, it is the best option for a no-date 40mm sub.
For identification against the genuine and other clone 3135 movements, note the position of the beat adjustor arm (red arrow) and the regulator arm (green arrow). Note the type and quality of the balance shock absorber setting (blue arrow). Note that there's a difference between the VS3135 used in VSF watches and the VS3135 used in CF watches: the version used in CF watches doesn't have a serial number engraved into the main plate.
This movement used to be exclusive to VS Factory (VSF), but is now widely available and replacements are available on eBay and AliExpress for around $130 USD.
VR3135 & VR3130
This is another good option for 40mm submariners. The part finishing and engraving is good. This is the second best clone of the 3135 movement. Note, there is a no-date version of the VR3135 called the VR3130. The VR3130 is a good quality no-date movement, second only to the VS3130. It's worth knowing that unlike the VS3135 (and gen) movement, the VR3135 doesn't have a shock setting for the escape wheel; this will reduce the shock resistance of the movement and is one of the reasons that the VS3135 is considered a better choice over the vr3135.
For identification of the VR3135 movement there is an easy way to tell it apart from the VS3135, on the VR3135 the hairspring is mounted counter-clockwise (purple arrow). The beat adjustor (red arrow) also has a black dot on it. But the regulator arm (green arrow) and the shock setting (blue arrow) look very similar to the vs3135.
Please note that there is a second version of the vr3135 which has a fake beat adjustor (blue arrow), and has the real beat adjustor (red arrow) and regulator arm (green arrow) pointing inwards. This is a style that is also seen in the VR3235 movement.
This movement is used in 40mm submariners from many replica watch factories. It is also available for purchase on eBay and AliExpress as a replacement for a broken movement for around $80 USD.
For anyone who wants a super deep dive into the Gen vs. Dandong (VS) vs. VR3135 movement,
@steve_theonewatches did an
amazing part by part macro photo comparison of the movements.
SH3135 & SH3130 (AR3130)
This movement has very low quality finishing. The hairpspring is mounted counter clockwise. Avoid this movement if possible. There is also a no-date version of this movement called the SH3130 (or sometimes the AR3130) which is of similarly poor quality. Avoid both the SH3135 and SH3130 (AR3130).
For identification purposes, not the style of the beat adjustor arm with the screw on the side (red arrow), the regulator arm (green arrow), and the style steel (not brass) cup for the shock setting (blue arrow).
SA3135 & SA3130
This movement has reasonable quality of part finishing, but poor quality engraving. The hairspring mounted clockwise. Go with the VR or VS movement if you have the choice or budget. There is a no-date version of this movement called the SA3130, which is of similar quality to the SA3135; as such a better choice for a no-date 40mm submariner is the VS3130 or VR3130.
For identification purposes note the round head on the beat adjustor arm (red arrow), the style of the regulator arm (green arrow), and the style and metal (steel) of the shock setting (blue arrow).
A2824
This isn’t a clone of a Rolex movement, rather it is an Asian clone of an ETA 2824 movement. There are quite a few variations on this movement since it has been around for decades and every movement factory in China has a clone version of it. This movement is reliable and easy to service and get replacement parts for. However, it doesn’t even remotely resemble what you’d find inside a Rolex. If you don’t care about what movement powers your rep, this isn’t a bad option. Complete Clone 2824 movements can be purchased on eBay and AliExpress for $20 to $50 USD. A genuine Swiss ETA 2824 will cost over $200 USD and will be a simple drop-in replacement for an Asian 2824.
For identification purposes, note the position of the beat adjustor (red arrow), the regulator arm (dark green arrow), the fine tuning rate adjustor (light green arrow), the shock absorber (blue arrow, NB: there are many different styles of shock absorbers on different clones of the eta 2824, the one in the picture is a lower end one), and finally note that the rotor runs on ball bearings (orange arrow).
A2836
This is another clone of an ETA movement that is never found inside a real Rolex. This movement is also reliable and easy to service. Some people prefer these movements since they are easy to fix or replace and “nobody can see inside my rep submariner”... the functions at the crown i.e. the direction you have to twist to set the date / time, will not necessarily be the same as on a cloned movement. Also this is a strange choice for a movement in a submariner since it has the functionality for both a day and date function, so it is more often seen in reps of the Rolex DayDate.
For identification purposes, this movement looks the same as the 2824 from the balance side, so there really aren't any easy ways to differentiate the two without looking at the keyless works or dial side of the movement. The pic below is here more for reference and the coloured arrows point to the same features noted in the description of the 2824 above.
41mm Submariners (1266XX) and 36mm and 41mm Datejust
There are several clones of the Rolex 3235 movement which appear in 41mm Subs, and 36mm & 41mm Datejusts. Please note: There are two version of the genuine Rolex 3235 movement which have slightly different sized date wheels. This is because the date window on the dial of the 41mm DJ is further out than the date window on the 41mm Submariner. If you are buying a replacement 3235 movement, be sure you get the correct version for your watch.
It’s worth noting that there are some 36mm Datejusts that use the VR3235 movement (e.g. the ones from Clean Factory), and the ones from VS Factory (VSF) use the excellent VS3235 movement. However, the majority of non CF or VSF 36mm DJs use an ETA clone. Unfortunately, the 3235 movement is too big for the 31mm Datejust case, so all replica 31mm Datejusts use lower end Asian clones of ETA movements. This is just a function of market pressure: there’s not a lot of demand for replica watches in lady sizes.
Genuine Rolex Caliber 3235
The genuine Rolex caliber 3235 is a relatively new movement with an astonishing 72 hour power reserve. Just like the genuine 3135 the genuine 3235 doesn’t have a regulation arm on the balance bridge (there is only a beat adjustor arm -- red arrow) since the movement is regulated by adjusting micro screw weights on the rim of the balance wheel (green arrows). All the replica 3235 movements have a regulation arm, so you’ll always see two arms on the rep movement balance bridges. Also note that the automatic rotor runs on ball bearings (blue arrow). Furthermore, the escape wheel on the gen movement is skeletonized (orange arrow), whereas it is solid on all the replicas of this movement.
VS3235
This is an incredible movement that is currently only available in VS Factory (VSF) subs and DJs. The movement has an amazing 70+ hour power reserve and is part compatible with the genuine Rolex movement. This means that it’s possible to swap gen parts into this movement to improve it. A common part swap on this movement is to replace the balance complete, pallet fork, and escape wheel with gen parts. With those parts swapped, the movement is virtually indistinguishable from the genuine caliber.
For identifications of this movement, look at the position of the two arms coming off the balance bridge (beat adjustor -- red arrow, and regulator arm -- green arrow): on the VS movement they face outwards. Also note the paraflex shock setting spring (blue arrow). The paraflex shock setting on the VS3235 movement is the actual functional shock setting, unlike on the VR3235 where the paraflex shock setting is simply a decoration plate.
Note: there is currently no non-date version of the VS3235, that is a "VS3230" movement doesn't exist (as of March 2023). There is however a
mod that allows for the removal of the phantom date correction crown position from the VS3235 and convert it into a true 3230 clone (i.e. only two crown positions: winding and time setting). The best option for an Oyster Perpetual or 41mm no-date submariner is the VSF rep with the VS3235 modded to remove the middle date correction position. The second best option is a OP or 41mm no-date sub with a VR3230 movement (see below).
Also note that is is not possible to buy this movement on eBay or AliExpress. However, if you have a VSF sub or dj with a broken movement, there are many rep-friendly watch smiths who will be happy to swap in a VR3235 movement for you and take the broken VS3235 off your hands for spare parts.
VR3235
This is a very common movement that is used in Subs and DJs from many different factories. This movement is technically not a clone but more of a hybrid between a 3135 and 3235 movement. This movement is reliable, although it doesn’t have the same power reserve of the VS3235, at only around 40 hours. While spare parts for this movement can be hard to find, a replacement movement is only around $100 USD on AliExpress, so it’s often more economical to replace the movement with a new one rather than service an old one.
This movement is easy to identify because it has a “fake” beat adjuster arm pointing outwards from the balance bridge (blue arrow), but the two functional arms (beat adjustor -- red arrow, and regulator arm -- green arrow) are hidden underneath the balance bridge and face inwards. Also of note, the end-shake adjustment screw on the balance bridge (purple arrow) isn’t functional, so adjusting the end-shake of the balance needs to be done with foil shims. The end shake adjustment screw simply secures a decoration plate that houses the fake paraflex shock setting (orange arrow), there is a real shock setting under this decoration plate.
Note: there is a no-date version of this movement called the VR3230 which is used on Clean Factory (CF) no-date 41mm submariners (as of August 2022). The VR3230 is the best option for a clone movement in a no-date 41mm submariner.
SA3235
This movement appears in some DJ41s and DJ36s. This is not a great movement, and should be avoided. The movement is decorated with poor quality plates. In the images it’s possible to see paint flaking off of the “reversing wheels” of the automatic model.
This movement can easily be identified by the decoration at the center of the rotor that is trying to make it look like the rotor runs on ball bearings like the gen 3235 (red arrow). Furthermore, the shock setting spring (blue arrow) on the balance bridge is a three sided closed spring vs. the paraflex springs that are present on the gen, VS and VR (although on the VR the paraflex spring is part of a decoration plate, and the real shock setting can be found underneath). This is a movement to avoid.
GMT Movements
For GMT movements, there are movements that have the correct hand stack (CHS) and incorrect hand stack (ICHS) on modern (6-digit) GMT models (1167XX, and 1267XX). Correct hand stack means that the hour hand is on the bottom, the GMT hand is next, then the minute hand, and the seconds hand is on top. Incorrect Hand Stack means that the GMT hand is on the bottom, the hour hand is on top of the GMT hand, then the minute hand, and the seconds hand on top.
Details on each movement are provided below, but this graphic (by
@KJ2020) is a shortcut to helping ID each of the 318X series movements movements. Note: There are two "true" 3285 clone movements which are (as of summer 2023) starting to see widespread adoption by rep factories. With these two new 3285 movements (see bottom of the GMT movement section) hopefully the days of trying to figure out exactly which GMT movement is the watch you're buying (to avoid the time-bomb movements) will be a thing of the past.
Hat tip to RWI's Gandalf the Grey of GMT movements:
@KJ2020 who helped me correctly identify each of the myriad clone GMT movements -- Thank you for helping me get this right.
VR3186 (Correct Hand Stack)
C'est un bon mouvement. Le VR3186 est fiable et dispose d’un mécanisme de saut d’aiguille des heures solide. Le VR3186 est parfois gravé du numéro 3285 (flèche noire), mais c'est le même mouvement. Ci-dessous deux photos montrant le même mouvement avec une gravure différente. Notez que ce mouvement est facilement identifiable par la position des bras sur le pont du balancier : le régleur de battement (flèche rouge) et le bras régulateur (flèche verte) pointent vers l'intérieur et il y a un faux bras de réglage de battement (flèche bleue) tourné vers l'extérieur. Notez également qu'un véritable mouvement clone 3285 (voir ci-dessous) a un rotor qui fonctionne sur des roulements à billes et non un pivot bijou (flèche violette) et a un réglage d'amortisseur paraflex (flèche orange) et non un réglage d'amortisseur kif.
A noter qu'il existe des mouvements VR3186 qui ont été gravés des chiffres "3285" (flèche noire) mais ils sont VR3186 dans tout le reste.
Notez également qu'il existe une ancienne version du VR3186 (parfois appelée VR3185 ou VR3186 v1) dont le bras de réglage du rythme et le bras du régulateur sont tournés vers l'extérieur. Cette version du mouvement peut être identifiée en inspectant le pont du balancier : le régleur de battement dont la vis du spiral pointe vers l'extrémité du bras (flèche rouge) et le bras régulateur (flèche verte) pointe vers l'extérieur (contrairement au VR3186 plus récent). De plus, le réglage de l'amortisseur comporte une coupelle en laiton (flèche bleue).
Pour toute personne intéressée par une analyse approfondie,
@CTime a préparé une
comparaison partie par partie du VR3186 par rapport à la génération .
SH3186 (pile de main correcte)
Il s’agit d’un mouvement de bombe à retardement qu’il convient d’éviter. Le mécanisme de saut de l’aiguille des heures est faible sur ce mouvement et a tendance à se briser. De plus, le mécanisme de saut de l'aiguille des heures n'est pas spécifique à la génération, il ne peut donc pas être réparé avec des pièces de génération. Ce mouvement est à nouveau identifiable par la position du bras de réglage de battement (flèche rouge, noter la position de la vis du spiral sur le côté du bras de réglage de battement contrairement à l'ancienne version du VR3186 où cette vis se trouve à l'extrémité du bras de réglage de battement. bras), et le bras régulateur (flèche verte) sur le pont de balancier. De plus, contrairement à l'ancienne version du VR3186, le SH3186 possède une coupelle en acier pour le réglage des amortisseurs du pont de balancier (flèche bleue).
SA3186 (pile de main correcte)
C’est un autre mouvement de bombe à retardement. Comme le SH3186, ce mouvement possède un mécanisme de saut d’aiguille des heures faible et doit être évité. Ce mouvement est facile à identifier car contrairement à tous les autres mouvements CHS GMT, son spiral est monté dans le sens des aiguilles d'une montre - cela signifie que le réglage de battement (flèche rouge) et le régulateur (flèche verte) sont inversés par rapport au VR3186 et au SH3186. De plus, le réglage des amortisseurs de ce mouvement est doté d'une coupelle en acier (flèche bleue).
SA3285 (pile de main correcte)
In 2020, GMF released a movement called the SA3285 which was basically a slightly different version of the SA3186. This movement can be identified by the beat adjustor arm (red arrow), regulator arm (green arrow), and shock setting (orange arrow) that are the same as the SA3186. However, the SA3285 had holes drilled around the rotor mounting (blew arrow) to make it look like the rotor was running on ball bearings like a true 3285 movement (see below). This movement is of similar inferior quality as the SA3186, so it should be avoided.
A3186 (Incorrect Hand Stack)
This isn’t a clone of a rolex movement, but rather a clone of an ETA movement that is decorated to look like a rolex movement. ETA GMT movements are reliable and inexpensive to service and repair, however, the functionality does not match the Rolex GMT calibers. A better option is the VR3186. The movement is easy to identify by the shock setting (red arrow), the ETA style winding works (green arrow), and the ETA style reversing wheels (blue arrow).
A2836 (Incorrect Hand Stack)
It’s unclear why this movement is labeled as an Asian clone of the ETA 2836, since the ETA 2836 is not a GMT movement. It’s more likely that this is a clone of the ETA 2893 movement. Nonetheless, this movement is not going to function like a genuine Rolex GMT movement, and has the wrong hand stack on the dial. A far better option is to go with the VR3186. This movement is easy to identify from the ETA style balance cock assembly (red arrow).
SH3285 aka VR3285 (Correct Hand Stack)
This is a new movement (as of March 2023) which has started to appear in C+ Factory GMTs and Explorer IIs. There is little long term reliability information about this movement, although
@CTime posted an
excellent photo comparison of the SH3285 with the DD3285 and the Gen 3285. This movement appears to be based on the VR3235 movement (discussed above), as such it is not a true clone but rather a hybrid that has both 31XX style parts and 32XX style parts.
There have been some
reliability issues reported with the SH3285 movement. Furthermore, the SH3285 appears to have
subtly different sized / position parts compared to both the VR3235 movement (with which it shares its train wheel and escapement design), and the gen/DD3285.
The SH3285 can be easily identified by the position of the beat adjustor (red arrow) and regulator arm (green arrow) which face inwards and the fake beat adjustor arm (blue arrow) which faces outwards. Additionally, the end-shake adjustor screw (purple arrow) is not functional, but simply secures a decoration plate which contains a fake paraflex shock setting (orange arrow). Also, unlike the 3186 movement, the SH3285 movement's rotor runs on ball bearings (pink arrow).
DD3285 aka CF3285 (Correct Hand Stack)
This is a new movement from Dandong movement factory (one of the best rep movement factories in China). This movement will apparently be exclusive to Clean Factory (CF). Based on the photo comparison posted above by
@CTime, the DD3285 appears to be based on the excellent VS3235 movement, so it is likely that it will have the long 70 hour power reserve.
This movement can be easily distinguished from the SH3285 above by the position of the beat adjustor arm (red arrow), and regulator arm (green arrow) which both point outwards and are very similar to the VS3235 movement from which the DD3285 is based. Also note the functional paraflex shock setting (purple arrow) and that the rotor runs on ball bearings (blue arrow) unlike clones of the 3186 movement.
DayDate Movements
Prior to September 2023, the only movement available for DayDate movements was the asian clone of the ETA 2836 movement (see above for images of the clone ETA 2824 movement since the 2836 looks the same from the balance side). The ETA clone is reliable and easy to service, however it doesn't operate in the same way as the gen 3255 movement from the crown. As such, for those looking for a closer to gen rep, there has always been a desire for a clone 3255 movement. This wish appears to have been granted in the form of a 3255 clone movement that looks like it is based on the reliable (albeit not a true clone) VR3235 movement from Shanghai movement factory.
VR3255
This movement is new as of September 2023 and has only (so far) appeared in DayDates from EWF. The movement looks like it comes from Shanghai movement factory and appears very similar to the SH3285 (GMT) movement and the VR3235 movement. All of these movements share the same inward facing beat adjustor arm (green arrow) and regulator arm (red arrow), with a fake hairspring stud pointing outwards (blue arrow). This movement also appears to have the same non-functional balance end-shake adjustor (magenta arrow) which doesn't adjust end-shake, but rather simply secures the decoration plate on top of the balance bridge. The movement is identifiable by the 3255 engraving (black arrow). As of this update, there is no information about the reliability of this movement, but we should expect that like most new movements (e.g. the SH3285) it will take a few iterations to work out the bugs.
Daytona Movements
There are two clone 4130 movements: the original Dandong 4130 movement used by Noob (until Noob was shut down in a raid in 2021), and now used by CF, BTF, QF, and "new Noob". But in June 2023 Shanghai Movement factory released a version of the 4130 movement (called the SH4130). These two movements (and the ETA 7750 which is used in lower end Daytona clones) are discussed below.
Dandong 4130 (aka DD4130 or "Noob 4130")
This movement is also known as the Noob4130 / N4130 / Dandong 4130. They are all the same. This movement is one of the highest quality replica movements available. For a long time it was exclusively available to Noob Factory. When Noob was raided and shut down in 2021, this movement disappeared from the rep scene. However, in early 2022 Clean Factory (CF), and then Better Factory (BTF), and Q Factory (QF) started making Daytonas with this movement. Daytonas with this movement are more expensive than Daytonas with a 7750 movement. However, if you care about the reliability and longevity of your rep, go for the DD4130. It’s worth the extra cost.
The DD4130 movement is also compatible with genuine Rolex parts. It’s common to replace the balance-complete, and the chronograph seconds wheel to build a movement that is nearly indistinguishable from the genuine Rolex caliber 4130. For anyone interested in a
part by part macro photo comparison between the gen and Dandong 4130 movement,
@CTime did the heavy lifting for you.
The DD4130 looks completely different from the 7750, learn to tell the two apart so that you can validate any claims made by a seller. Easy parts to look for when identifying a DD4130 vs. a 7750 are that the DD4130 has three screws securing the rotor (green arrow), a column wheel (red arrow), and a balance bridge (blue arrow) rather than a balance cock.
Skeletonized Dandong 4130
There is a version of the Dandon 4130 which has been skeletonized and is used in several special editions of the Daytona which are produced by SONIC Factory in China. The Skeletonized version of the DD4130 is easily identifiable as a derivative of the Dandong 4130 movement due to the position of the beat adjustor (red arrow) and regulator (green arrow) arms on the balance bridge. In addition, the skeletonized version of this movement has many parts of the bridges and rotor which have been hollowed out (blue arrows). While this is an interesting and unique movement, the level of finishing isn't the same as the "gen" version which is customized by
Artisans De Geneve. Nonetheless, this is an excellent movement and a beautiful piece for any dedicated Daytona rep collector.
Shanghai 4130
In June 2023 Shanghai Movement factory released a 4130 clone movement. As of June 2023 we have only seen this movement in Daytona reps from APSF (a factory known for their high end AP reps). There is no reliability information available as of this update. However, for now, there is an easy way to differentiate the SH4130 from the DD4130: The position and style of the beat and regulator arms on the balance bridge. Unlike the DD4130 where the beat and regulator arms point outwards, on the SH4130 the beat adjustor (red arrow) and regulator (green arrow) point inwards. Furthermore, on the SH4130 there is a fake hairspring stud (blue arrow). This style of balance bridge is common on other Shanghai clone movements such as the VR3135, VR3186, and SH/VR3285.
Shanghai 4131
At the end of December 2023, we saw the release of a 126500 Daytona from AR+F which uses a customized version of the Shanghai 4130 movement. This 4131 movement appears to be based on a SH4130 due to the beat adjustor (red arrow) and regulator (green arrow) arms. However, this version of the movement has been engraved with the "4131" caliber number (blue arrow). And it has a different rotor that has two large cutouts (purple arrow). However, it doesn't have an updated shock setting (yellow arrow) -- the gen 4131 uses the new paraflex shock spring rather than the older incabloc style spring. However, there are some mechanical updates to this movement which show that it's not simply a redecorated 4130. There are three visible changes in the SH4131 from the SH4130: 1) The column wheel is different (black arrow), 2) the vertical clutch jaws and spring is different (cyan arrow), and 3) the hammer spring has been peened (orange arrow).
7750
This is an Asian clone of an ETA 7750 movement. The reason that this movement isn’t great for the Daytona is because it is thicker than the 4130 movement, so the movement is often slimmed down (and thus made less reliable) to fit inside a 12.4mm thick Daytona case. Furthermore, the Daytona has its small seconds at 6 o’clock, but this is not the default position for the small seconds complication on the 7750 movement; various additional wheels need to be added to the top of the 7750 movement to get everything into the correct position. This complication adds stress to the movement and reduces reliability. With the clone 4130 widely available, it's a good idea to avoid Daytonas with the 7750 movement.
The 7750 can be identified by the single screw securing the rotor (red arrow), and the balance cock (green arrow) vs. the balance bridge see on the 4130.