It looks like the earlier/regular thick case. If it is, then it should have a dial without '1000' on the dial, so my best guess is that this has had new dial and movement.. Essentially a 'put together'.
Now, it is possible that it is a 'crossover' transitional watch, between the switchover from thick to thinner case.. But in this case, probably highly unlikely, given that it has incorrect caseback, crown and movement.

If I were you, I'd fit the eta movement listed abov, possibly a crown and be done with it.
Finding a caseback won't be easy, and at the end of the day, with (technically) an incorrect dial, it's not a big problem, if that makes sense.

Now, you might be feeling a bit downbeat about it.. But this is a nice looking diver, and with a correct movement it will be a nice watch. Sure, not 'catalogue' correct, but who cares, if you're going to wear it and enjoy it.
Stewart