Info on my estate find 1940's Omega Automatic

I picked this up at an estate this past week, and I can't find anything about it. I do think it has a new crown, not Omega, but the crystal and the dial look original along with the luminous baton fine point hands.
The band was a simple Hadley stainless stretch that I removed, though in remarkably good shape.
Looks to be from the mid to late 1940's and the one big question I have is how to I remove the back to see what movement it has. It is a bumper automatic, and the watch does run and hold time.
I took it to a jeweler that has years of experience with watches and he said it maybe a top loader movement, then someone mentioned there is a bezel on the back case, all I know I am stumped. Any help would be apprecited.

That sounds like a very smart move, any idea of what movement would be in it or for that matter is it rare or worth more than a few hundred dollars?

OK, that is interesting, so the 30.10 RA movement on that watch has a smaller second hand not on the center wheel pivot, would the one I am asking about use a variation of that movement?