Tbh, exhibition casebacks in that price range becomes boring cause the movements arent that nice (most of times just a nice rotor at best).
The only really nice movements to look at are the Seagull chronos, that’s worth having a caseback for.
Anyways, it doesn’t matter cause most of watches have an open caseback anyways as that’s what most of people want.
A nice office watch with a nice caseback is a Tissot Lelocle, which is in your price range. Recommend to buy it on a bracelet, if you buy on a strap you will need to change the strap (19mm), cause the OEM is crap.
Good watch and movement, banger for buck!