I read the movement is Lemania 872 (Same as Omega 860)...which is legit for this case (the monopusher version would be 2220, my bad) the caseback doesn’t look like I would expect, but I can’t say I have seen an Omega dial in such a case ...only military issued Lemania.
Just a put together. Will have an inner movement cover. I have a NOS Spare case like that. These cases were sold a few years ago by Watchco. Kind regards. Achim