Seeking info on two PROM chips.

Does anyone have details on the following ROM or PROM chips from a DEC VAXstation 4000 VLC? Their identifying numbers are LUP9327580 (DEC part# 23-286E8-00) and LUP9331604 (DEC part# 23-287E8-00); they're each 40-pin DIPs. The U's may actually be O's or 0's; it's difficult to tell given the DEC part number label placement. I'm assuming they're programmable as I believe I managed to stomp on a writeable area of the chips, rendering the boot console code they hold non-functional. Fortunately, they're sitting in sockets. And also fortunately, I've another system with functional versions of the same. I'm interested in finding out more details about what their specs are, and the possibilities for either reprogramming them or equivalent parts. Thanks. -brian.