Here's a viewer magnifier that pinches in behind the eyepiece ring on the original F-1 and F-1n (but not the F-1N aka F-1 New). It has a bracket that gets pinched in, and then the magnifier can either latch into place over the viewfinder window, or flip up out of the way for normal viewing. Obviously this is for use with the standard prism, not the Speed Finder. I'd like to get $30 for this, but that includes shipping anywhere in the world.
Duncan
Duncan