I just asked, and here's the reply I got:
"Some guy purchased all of these items at an estate sale for a guy that had a shop in the 70's/80's that closed down. He wouldn't tell us what shop but said that after the store closed the guy just put all this stuff in his basement. There was a lot more than just the Sunn amps. The 2000s and 2x15 in the box just sold last week."
I wish I would've been at that estate sale!