Got this today. Rather special for me, (although there's a Patek and a Breguet to compete with.)
14 carat gold case by Trusty - which was a brand of Schwob Freres as was Cyma.
I think its a Jean Finger patent case, 1921 see The Development of the Waterproof Watch although it doesn't say so. With these designs, the bezel screws off to give access to the movement which is on a hinge to allow for setting and winding but otherwise is sealed against the elements.
The back is engraved E.O. Johnson
And I think its got a Cyma 30 inside - running and keeping time and yes I can see that the regulator has been pushed right over.