Looks gen from the pics. Check the serial number in between the lugs on the case and see if it coincides with what the seller says about the year of origin. 1990 should be an E serial, but sometimes watches are made a year or two before they sell. The 16710 was introduced in 1989 so the only other older serial this could be is an L serial from 1989. Ask about the history of the watch and if there are box and papers.
https://www.bobswatches.com/rolex-serial-numbers
The bracelet looks like a 93150 and same for the clasp. These are technically Submariner parts, and the clasp has four stamped "links" instead of three on the 78790A clasp the GMT and Explorer II came with. The clasp originally came with a dive extension but some owners remove those. If removed, another connector link would have had to be sourced to keep the bracelet and clasp together. This part is often not gen.
Rolex did issue the 93150 bracelet and clasp with early 16710s and 16570s. My 1989 came that way and it was a very good thing because it only had 10 links and it would not have fit me without the longer 93150 clasp.
Lots of pics of my gen in this thread
16710 BP vs Gen
As others have said, the price on this is WAY low so get the movement looked at and if it were me I would have the watch authenticated by an AD watchmaker. This is a steal in either of two scenarios. Just don't let the victim be you.