Summary

This is a bezel cover which fits newer GMT Master, Submariner, and other watches with a 41mm bezel.
It is a work in progress as I want to add marked five minute blocks, and one minute hashes.
This bezel cap protects the watch from damage, it possibly also disguises an expensive watch with some plastic if traveling in a high crime area without reducing the timekeeping functionality.

Instructions

Print at 10% and press fit onto newer GMT Master, Submariner, or similar 41mm outside diameter bezel, adjust the .scad file to fit your watch, bezel should still turn when installed.
This can be adapted to make a bezel puller or as I plan to do, add hashes every 30 degrees that can be filled with luminous paint to allow me to use the minute hand to time events like most dive watches have. The GMT Master has a 24 hour hand and 24hr bezel for calculating timezones rather than a 60 min scale bezel but it is still a great dive watch, this allows GMT owners tohave a divers bezel when needed as well rather than having to bring another watch just for divinghi. This currently protects from banging the ceramic bezel or drops onto stone surfaces.
I have figured out the math to plot the minute hashes on openSCAD so it is only a matter of time now.

Bezel cover