Identifying old HP iron

Hello, I've got an old HP system that I rescued from ebay. I've asked in german newsgroups but that and googling did turn up next to nothing. It's a beige machine of the stackable kind and I think I've seen Series 300 machines with Motorola CPUs in a similar enclosure. What I've got along with some HP-IB cables and a 700/92 HP terminal is: * 7957 Harddisk. This spins up and the light on the front turns green. * 9144 Tape Drive. I get some status codes on the display on the back but as long as I don't get the system up that doesn't matter very much I guess. * The main unit is labelled "HP Series 40 260" on the front. It seems to have a 5 slot backplane of some kind. 2 Slots ar occupied by the mainboard which has little else than two serial connectors. Then there is a HP-IB interface and a serial card with 3 "normal" ports and a fourth that looks somewhat like the DIN headphone connectors on audio equipment. The uppermost (fifth) slot is empty. There is a small info card in the back that informs me that the system is model "45072A". So what is this? Is this a "260" as in "successor to the 250"? The first followup question to that would be asking what the appropriate terminal settings are for connecting to that iron. I do get something on "PORT-1" of the main logic board, but no setting (from 9600 8N1 to obscure guesses as 1200 6N2) nothing yields useable results. Gerhard