+1 on the Cammenga military compass.It is a dry cell compass and air bubbles is one of the reasons the military uses them. They go from high altitude parachute drops to sea level landings with no ill affects.
I live in a neighboring county where the Cammenga company is located.I even applied for work there.Cammenga is a small company that has great customer service.The owner of the company personally dealt with me when I applied.Regretably they were not hiring.
We talked for an hour on compasses and my use of them in them in the military.I bought one years before and could tell it would be a good company to work for.They make a solid product(nearly bombproof)that has been passed on from father's to son's.
So no affiliation with them(but would like to have)and just a happy customer...

BOATMAN
John