Hi Ed,
Sorry it took me so long to reply, but I just now found your posts about the Croton casebacks. Anyway, yeah, I've just about given up trying to find these darned things, as that awfully thin lip on 'em is just impossible, to work with. I had thought perhaps I could get something "fairly" close, i.e., crimping a 29mm caseback inward just a bit, but, with that nearly-nonexistent lip on the case, and plastic at that, it just would NOT grab ahold, and stay on. Nor, would trying to "flare-out" a 27mm caseback, do the trick;...it just wouldn't stay on. I also thought of possibly going to a metal-working shop, to see if they could make a couple of casebacks from scratch, as I'm fairly certain that the original ones were simply pressed aluminum or tin;...that is, very cheaply made, like, the ones you'd see on a plastic-cased Bowmar, for example...very cheap, die-cast or pressed tin, sometimes with no writing at all, embossed onto it.
..Anyway, thank you for your efforts in trying to locate a couple casebacks, I appreciate it!
Cheers,
Charles