FWIW, I have fired both the .32 and .380 Stop and the .380 Baby with American ammo and they worked. That is not to say any particular gun will do so, but mine did.
In all honesty, though, those guns are old, not that sturdy, and parts are non-existent, so I suggest not firing them. They are a fairly valuable collectors' item today, and if anything breaks, that value will be affected.
Jim