Here are the simple steps to clean a 1951 Nikon S Rangefinder camera. I’ve read that the Nikon One and Nikon M are similar except for the Accessory shoe does not need to be removed on the S. Also the film advance knob does not need to be removed, but for cleaning, simple loosen the set screw and unscrew the knob (ccw)
I recently acquired a 1957 Canon L2 from a fellow in Japan. As the listing stated, it is fully functional in every way. It is a joy to use. Smooth, well built, balanced. It’s only flaw is the same as every camera I’ve gotten, Hazy viewfinder. I did some research and found not much at all on this model but similar models share the same rangefinder set up, but the top plate is slightly different on them. The following is the method I used to get at the insides of the top plate.
start by removing the front RF collar. It unscrews counter clockwise (ccw) with just your fingers After removing the collar, remove the lens, it should be tight but it just slips out and under that is a ring that holds the lens. A spanner wrench is required to remove it. The lens has spanner slots too, this can be aligned with the ring underneath and both unscrewed at the same time if you have the right tool. Also the lens spanner slots makes it possible to realign the vertical RF image by rotating it until the image is correct.