hmm. picture in mckeown's does't look like any of the shown -- simple molded bakelite camera but sometimes fitted with leica lenses?, Looking at the prices for those things I'd say you want to be very careful about messing with it.

i am going to guess -- the pic in mckeown's doesn't show enough -- that the bottom comes off somehow, a la Leica. Should be a small switch there, or push button or something. If you can't figure it out by gentle pushing and nudging, set it on the shelf and find a different camera to shoot with.