I have lots of warehouse space so I save anything "collectable" that looks good including the Zinscos, FRE's, 2pole70 plus, all mains, bolt ons and all 3 phase breakers.
Unless they are brand spanking new, I don't bother with standard QP, MP,CH or HO's because they are less than 4 bucks a pole new. I only go to the archives occaisionally. I did use a twin 15 Zinsco the other day.
I still have a few deltas breakers that pick up A and B phases from the bus and the high leg is fed thru. They were popular here in the early late 50's for 3 phase AC's.