The watch looks like a genuine article to me. Probably from 1960's, Tissot caliber 782? manual movement. The crown should have the "T" sign but I can't see it from the photos you provided.
You should ask the seller for an image of the dial without the scratched plexi so you can see what it's really like. There is also a post here you can read about Tissot Seastar: https://forums.watchuseek.com/f11/tissot-seastar-what-am-i-missing-526908.html
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