Any idea what kind of gun or magazine can accept the 7.62x25 stripper clips?
They are identical to the strippers for the 1907 Roth-Steyr.
Rather than come up with a new charger design to load their SMG magazines, the Czechs evidently decided to use the existing tooling for these chargers and make their magazine loaders work with them.
About 30 years ago I bought a big bunch of this early 50's Czech 7.62X25 in the same boxes, on the same chargers. My experience with the ammunition is that I would get one or two no-fires out of a box, and occasionally you would need to drop the hammer twice to get some rounds to go off in my Russian TT33.
By the way, When I bought the 7.62X25, I bought a bunch of very similarly constructed and packaged 9X19 ammunition. The big difference in the packaging was the chargers for the 9mm were chrome-plated instead of being parked. Don't ask me why.
The 9mm I bought had about the same fairly minor reliability issues as the 7.62X25.