You can ask whether a watch you bought is real or not. I bought a Seiko diver at the old US Navy base in Subic Bay Philippines last year that appeared to be a nice Seiko pepsi diver.
However it had 24 jewels instead of 21. The thing is it had a hackable Seiko movement that Seiko sold to other watch makers such as Invicta. Since I had a Pepsi Invicta diver with the same Seiko movement (almost) already
I returned the "Seiko" and got the watch back. I had a street vendor open the watch just so I could take a picture of the movement and some idiot who responded to the thread thought I had bought the watch on the street corner.
One cool thing about Philippines is that basic watch repair and new batteries are available about 16 hours a day right on the streets in big cities.
Here is the thread. Beware the 24 Jewel Seiko pepsi diver! Shows you how little I knew about the Seiko divers then lol.
https://forums.watchuseek.com/f21/return-keep-seiko-nh36a-0020-scuba-divers-3979962.html