Lo and behold...here is 000271 - 7718 pots, 1 of 67 white FBs shipped in 1977. So # 000236 above must be another one of these.Then it should have 8 numbers - and I can see only six, like the older Kalamazoo style stamped numbers. But 000236? Does not seem to conform to the ranges at the time.
Is this serial # range already mentioned anywhere in the 'official' 1977 ranges (it may be, just axing)?