AIM65 with unknown second board

Afternoon... We were given an AIM65 the other day (first time I've seen a real one) in a rather fetching custom blue case that has a carry handle on one edge. It was apparently used by Xerox for some for of magnetic media testing way back when; it still carries a Xerox asset tag on the back. Unfortunately in between the previous owner saying they wanted it when it was retired and them going to collect it, it got thrown into a skip - so there's some damage to the case and the red display cover needs replacing. Luckily the electronics survived, apart from one broken switch. Curious thing about the machine is that it has a second board mounted under the main board, containing quite a bit of circuitry. I was wondering whether this second board is something custom produced by Xerox (there are no marks indicating manufacturer) or whether it was an official off-the-shelf expansion board... Quick and dirty pics at: http://www.moosenet.demon.co.uk/temp/comps/aim65/ Wish I'd brought the machine home now, but I can get a list of the main ICs on that second board when I'm next at the musuem if needs be. Note that there seems to be no RAM on the AIM65 board itself, - just ROM - but there are 16 4116 chips on the expansion board. cheers Jules