> unibus system; it also had some M8043 and M8017
cards in it so it must be
> something DECish? 
Those are qbus.  M8043 is a DLV11j 4 line serial and the M8017 is a DLV11-E
serial card.
 I've seen N8X305N somewhere recently, but I
can't remember what it is :-(
It's a Signetics part, if you want to search for it. 
It's a microcontroller used commonly in hard disk controllers as the cpu.
Allison