Its one of those cocktail watches from the eighties, very popular then among women. Looks (possibly) genuine, but it rings an alarm bell a white gold watch with an stainless steel back. To be sure you'll have to open the back and send us pics of the inside of the back and the movement. Also, taking it to a jeweler and testing the gold would be a good idea. I.E. look at this one:
https://www.swisswatchexpo.com/watc...dies-18k-White-Gold-2-ct-Diamond-Coctail-9606
The back is also gold.
Case back and movement are genuine and I believe the rest of the watch is as well.
Seems odd that the case back is marked 20-microns gold plate which is in stark contrast to the bracelet which is marked 18K 750. White gold isn't really all that white so the wear to the clasp could be honest as these were plated with rhodium to give it a bight "white" finish.
The weight would be a good tell as to the makeup of the case/bracelet.