I’m constantly searching these..
I use ‘dual-time’ ‘world-time’ ‘GMT’ ‘UTC’
Bell and Ross is good - likely on my list in the future.
I have a real soft-spot for the ‘Steve McQueen’ explorers.
Another vote for Sinn also.. I like the 144 with 12 hour GMT but could be a bit busy depending on your preference.
It can be done with a 12-hour rotating bezel also (obvs won’t tell you AM/PM).
The functionality of the movement can be important - whether you can set the main time without impacting the secondary - or vice versa.. in this respect it sounds like Rolex have this covered.
The ‘steel’ Casio world time watch also looks pretty good to be honest but not sure it displays 2 times concurrently— generally I prefer just to be able to glance down rather than press buttons to access the second time.
Wow - I’ve bored myself now! Let us know which direction you’re thinking.