A large % of LTM Leicas were factory updated you need to buy on serial and photos if you are a collector.
The only functional thing was have you got a baseplate finger near to the latch. This keeps the film in the rails.
Yeah, I'm pretty sure the one I have was originally a IIc, but was factory updated to IIIc specs. I heard it's quite common, and a lot of folks did it for a variety of reasons (to avoid high import taxes, update the mechanicals, etc). Nothing to get worked up about.