Well, I'm only 62. I have seen a few things in my day, but I don't recognize this one. Maybe it was not popular in my area. hopefully on of the old timers will recognize it.
It appears to be a Universal Rundle #962WB, but it could also be obsolete so you would have to check with a faucet parts dealer in your area for availablility. The seat should be good, so you don't have to worry about that.
I think I found it, I'm guessing stem is not the correct word, it's actually a cartridge. The little plastic piece dose does not move in and out but turns to block and unblock the flow of water.
The lenght is correct, and the drawing looks about right, should now it a few days.