The bezel ring around the crystal needs to be pried up and the crystal removed in order to access the movement/dial; but before you do that, the two-piece stem needs to be separated. This can be done with something rigid pressing against the back of the crown and forcing it outward, but best to leave that to someone who knows how to do this. Be careful with prying the bezel ring, as this chrome plated case will damage easily.
I think this one is a Seabee model - if the movement is 17 Jewels. The Seabee was advertised in 1953+. I've found ads for a similar 15 Jewel Watertite with full numeral dial through 1952, not sure if these were available in 53+. These were both with radium hands and dial and chrome case. The id may depend upon the jewel count, so verification of the movement will be very helpful.
1952 Watertite ad
