I was visiting a local(-ish) LGS this morning (great new-to-me LGS find, Clay Shooters Supply). They have an unfired, new 6520 in their shop. Unbelievable! Has some surface barrel rust from storage. Apparently was from a confiscated collection; still had the Dallas PD evidence tag attached to it.
I was going to buy it and tear it apart for the upper, but 1) it's a large pin lower and 2) couldn't bring myself to do that to such a pristine example.
5 years ago, I would have bought it just for the collection, but I'm divesting myself of those kinds of purchases.
Pretty sure its up on GB.