Re. 'the gumf on the display(s)'; That's the game i.d., consisting of its name, Williams project/model number (541, included on most unique parts) and the software revision, L-4. It appears when accessing the bookkeeping, and by default when the machine boots up if the battery is dead, and the door's closed. I doubt if that much would show if the Ram had actually failed, rather than just becoming corrupt due to battery failure.
P.s. I hadn't heard that query for nearly 30 years; a collector had called in that a Space Shuttle wasn't working when she counted the money in it. I found that one of the roms was loose, and brought back the coin meter readings, being asked "what's the '2535 6' mean when I press the button?" when I handed over the paper with them on.