now that's a rare one
both the watch and my answer, as most pieces posted are either questionable or clear frankenwatches or fakes.
this is a very nice and perfectly correct "spider lugs" Premier 797, even if the pics u post are so small I can't read the serial properly, all of these I've seen were produced between 1946 and 1947.
Movement is a Venus 175, bridge should be marked Breitling Premier.
Last auction sale I remember for a 797 ended a bit above $2k to give u a value estimate.
casebacks are easy to take off with the proper tools, but if u do not have that, I'd suggest to have a jeweller do it.
I see little to worry about, though verifying the movement is correctly marked does make sense.