Thank-you Top-Cat, for your detailed post; much appreciated! And thank-you Dave, for the filter info!
Yes, my camera is definitely a Perkeo 1. Regarding the double exposure prevention, my understanding is that the Perkeo 1's from 1951-52 did not have it, but they did from 1953-55. So your camera must be one of the earlier ones? I don't really know if it uses the very same system as the Perkeo 2, but I have been assured that mine is in perfect working order. (fingers crossed!)
While I await the arrival of my camera, I have been hunting onlne for a nice shoe-mount rangefinder, but they are quite expensive, and almost all that I have seen appear to be in less than ideal condition. So I think I will just manage without, as I have been doing with my other cameras. So it will be strictly old-school for me, right down to Sunny 16. Just the way I like things done!