Thanks K, that first link is awesome. I could spend days just looking at all those original manuals. No 520 though (rats!).
Nice pic Hawg. From all the searching I've been doing I think I may have actually learned something. I'm a long way from holding my own with anybody here, but there's hope.
From what I've been reading the top gun is a 520A? Squared receiver, shorter tangs with the safety mounted on the top tang.
Lower one looks just like mine except your forend is checkered, mine has vertical grooves. And of course, the evil inertial system.
Thanks guys, I really appreciate your input.