Rodney,
I have several non-Singer machines that use cams. Kenmores and others too. We're still cleaning up after the big storm last week. Our basement flooded and ..... well, no serious damage, but it's still drying out and things are stacked every which way. As soon as I can can get to it I'll try to do close ups of the cams and machine for the thread.
The Singer 319 is the only Singer I know of that has what is called type-writer keys on top. It also uses flat cams mounted on the side. Very interesting machine. No where near antique yet, but definitely vintage.
Joe