Did a threads keyword search in the forums here, which failed to narrow this down sufficiently, then spent about 20 minutes trying with Google. Anyway, so far I've found no trace of any Replay feature in an early 70's Williams table I just acquired, nor is it mentioned anywhere in the pdf manual I downloaded from IPDB. I had just assumed this feature was pretty much a given for all pins from at least 1970 on . . . as it is on my Bally Wizard ! from around this time, although that is user-adjustable. If the feature is indeed absent entirely, I don't suppose that can be remedied by some mod that is not a very major project ? (I'm fairly certain that the choice between having this Williams be a 3-ball or a 5-ball game *IS* user-adjustable.)
One other thing: the credits counter reel appears to be frozen. It's only been a few days, but so far I haven't managed to earn the 97,000 points or whatever it is for a replay, but neither has that counter decremented at all, over quite a few games, so it is clearly stuck. Not sure what to look for . . . .