I bought another 880 last week. It was local and the price was good. When I got home I was floored to discover that the serial number was 44126 - the one I owned before was 44125!
There's an extra hole on the front of the amp that has been plugged. On the inside, there is wiring leading to the hole (the seller showed me some photos he'd taken) but I haven't had time to take the top off and figure out what might have been there before.
So .... if anyone has an 880 faceplate to sell please let me know. Thanks!