That is a highly interesting Tissot 33.3, the dial layout is superb, so the rest of the watch !
These waterproof cases Tissot (and Lemania) are scarce among the 33.3/15TL powered chronographs range, it's hard to cross one hence the opportunity.
Now based on the photos, there are some elements that look questioning, some of them :
-over-inked Tissot script ?
-odd case back engraving ?
Here's one I have for years in my HD for comparison
but is that one correct ? I could not tell but what I can say is this one (if original) is the same found on some early waterproof cases Omega
-service pushers caps ?
pushers caps look tiny from here, they're crucial parts to respect the originality of these IMO, it seems they're impossible to find (?)
here's a reference photo showing the same case type with what I believe could be the right pushers caps
Please keep in mind all of these questions are assumptions, these are almost not documented, resources are rare and difficult to find so no certainties here, just questions.
In any case, it remains an attractive and not often seen vintage chronograph with this waterproof case type, thank you Blomman for posting this !
Best,
Laurent