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Building a GMT Master Ref. 16750 the successor of the Ref. 1675

matzemedia

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I am a big fan of the older GMT-Master and had built already the early 1675 with and without gilt dial. The Rolex GMT-Master Ref. 16750 is an iconic model in the history of Rolex, known for its distinctive features and evolution over time. So it is time for a new project. And because I had not found a lot of information about this reference here, I decided to join my journey.

Here's a detailed history of this specific reference:

Introduction
- Launch Year: The Rolex GMT-Master Ref. 16750 was introduced in 1979, as a successor to the Ref. 1675.
- Production Period: This reference was produced until approximately 1988.

Features and Innovations
- Movement: One of the significant upgrades in the Ref. 16750 was the introduction of the new caliber 3075 movement, which replaced the caliber 1575 in the Ref. 1675. The caliber 3075 brought the quickset date feature, allowing the wearer to change the date independently of the hour hand, which was a substantial convenience.
- Hacking Feature: The movement also included a hacking feature, which allows the second hand to stop when the crown is pulled out, enabling precise time setting.

Design and Aesthetics
- Dial: Early versions of the Ref. 16750 featured a matte dial with painted hour markers surrounded by tritium for luminescence. Later versions transitioned to glossy dials with applied white gold hour markers, a characteristic change seen in the mid-1980s.
- Case: The case remained 40mm in diameter, consistent with its predecessor, but featured improved water resistance of up to 100 meters (330 feet), an enhancement from the previous 50 meters. There is no big difference to the Ref.1675 with the exception of crown guard shape.
- Bezel: The Ref. 16750 continued to use the bidirectional rotating bezel with a 24-hour scale, an essential feature for tracking a second time zone. The bezel inserts came in the classic "Pepsi" (red and blue) as well as all-black versions.
- Transition Model: The Ref. 16750 is often considered a transitional model in the GMT-Master line, bridging the vintage characteristics of the Ref. 1675 with the more modern elements that would appear in subsequent models.

Here a picture of a gen 16750 and some advertising of the 1980's:

 

matzemedia

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I have already collected some parts for the project over the last few months. The parts collection consists of the following:
  • Movement: VR 3186 - Asian GMT Movement
  • Dial: Gen glossy tritium 16750 with applied hour markers
  • Hands: Aftermarket hands
  • Datedisc from ebay with open 6,9
  • Case: Raffel 1675
  • Crystal: Sternkreuz 302
Here how it lookes:
 
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matzemedia

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Fortunately, the housing of the 16750 is very similar to the 1675. According to my research, the crown guard in particular is different. Here are two pictures with a direct comparison. As you can see the 16750 has a more rounded crown guard. The 1675 crown guard is more edgy. Both use the 5.3 mm crown.

1675:


16750:


So the mission for tomorrow is to shape the Raffles case to get a 16750.
 
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ZX_RR

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Fascinating. I'd be interested to learn how you get the dial to fit the VR 3186 movement. What modifications may be involved to dial feet or to the movement foot slots/holes. Also if any adaptors needed position the dial at correct height in the case.
 

matzemedia

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Fascinating. I'd be interested to learn how you get the dial to fit the VR 3186 movement. What modifications may be involved to dial feet or to the movement foot slots/holes. Also if any adaptors needed position the dial at correct height in the case.
We will get to this part ;-) But let me give you a quick answer: It is just plug an play!
 
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matzemedia

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The Raffle 1675 case has a lot of material around the crown. That makes it so flexible to build different references. For example: if you like to shape the crown gard to a vintage 1675 with PCG you need a huge width.

The original Raffle 1675 case with the width crown guard:


I do the rough job by using a file. Just removing the material in slow steps. To be sure removing the material at the right spot, I searched for images of gen watches that reference and copy the shape. It is a timeconsuming job. Every minute I check if i am still creating the correct shape, compare the interim result with the images on the references. One risk is that you create a sloping surface with the file. This requires practice.

At this picture you can see I've done the curve or radius at the crown guard:


And here I have already reduced the width of the crown guard on one side (bottom).

Once I'm happy with the result, it's time to polish. The file leaves coarse grooves in the steel. The grooves can be reduced with less pressure on the file or a finer cut.

For polishing, I use sandpaper with a grit of 280 to 7000. The surface is already much smoother after using the 280 grit. With the 1000 grit (wet) you can already see a shine.
Normally, a polishing machine is used in the final pass. But I didn't bother with that.

Here some pictures of the new 16750 crown guard shape:
 

matzemedia

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Fitting the movement
The VR 3186 does not fit into the Raffle case. The diameter is about 1 mm too small. This is where my favourite tool comes into play: The latte. Here pictures say more than a thousand words.

The steam high is unfortunately not optimal but still within the tolerable range. Well, the Raffle case is made for ETA or NH movements, so it doesn't have the typical Rolex bolting. That's why I also use the standard movement holder.
 

matzemedia

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Relume Hands and mount everything together
The hands of the original 3075 movement also fit on the 3186 movement. Important for the Ref. 16750 is to use the slim hands and not the new wide hands. I was able to find the hands as aftermarket.

The 167XX dial still has tritium for the hour markers. This is not necessarily my favourite working material. I hope no crumbs were scattered around my workroom while I was working. I briefly considered using lume for the markers. But then I decided to leave the original - at best, the radiation has gone in the meantime.

As the markers have a nice ochre colour, the hands should match. With a little coffee and different acrylic colours, the tone is more or less matched. But that was really difficult for me to mix the right color.


 
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matzemedia

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Fascinating. I'd be interested to learn how you get the dial to fit the VR 3186 movement. What modifications may be involved to dial feet or to the movement foot slots/holes. Also if any adaptors needed position the dial at correct height in the case.
The VR 3186 movement and the 167XX dial have the same foot position. Both at 13 and 37 minutes. So there's no need to re-set the feed. The case is high enough to fit the 3186 movement. Only the steam height is critical - but it still works.
 

Spoons

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Following with interest. Thanks for sharing your work along the way.
 
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matzemedia

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The final result
It's time to lift the curtain. Here are a few pictures in the assembled state. I used a darker and already bleached insert. Unfortunately, I can no longer say exactly where it came from. It's been in my drawer for a few years.

I'm currently experimenting with different leather straps. The original version of reference 16750 is the 62510H (Jubilee) or the 78360 (Qyster). I've ordered another Jubilee steel bracelet from Raffles and I'm curious to see how it suits me.


Here three generation GMT Master in a row:
 

EnryDJ36

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The final result
It's time to lift the curtain. Here are a few pictures in the assembled state. I used a darker and already bleached insert. Unfortunately, I can no longer say exactly where it came from. It's been in my drawer for a few years.

I'm currently experimenting with different leather straps. The original version of reference 16750 is the 62510H (Jubilee) or the 78360 (Qyster). I've ordered another Jubilee steel bracelet from Raffles and I'm curious to see how it suits me.


Here three generation GMT Master in a row:
If you want my advice to improve it even more change the crown, Athaya or Gen and the insert with a Gen will change for the better.
 
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