[Recommendation Request] Exhibition caseback around $500

Hoping Reddit can steer me in the right direction with a few different options. I’m looking for an open/exhibition caseback mechanical (manual or auto) watch for my brother-in-law’s 30th birthday.

It would be an everyday wear, so something for the office (he is an engineer) as well as less formal at the weekend. Looking to spend up to $500, but could stretch if something perfect popped up. Like the look of the Nomos watches, but can’t stretch that far unfortunately.

What would you offer, if you were me?