Hello and thanks.
That's reassuring.
As it happens, mine is a Speedmaster, too. One of the TV Dial Mark IV's.
The auction house said that it had come from a good home and in with the watch is an instruction booklet for a Mark V, a few ebay listing sheets and a handwritten note from the deceased explaining that the watch was made in 1974 and first worn (by him) in 2010.
The discrepancy in the date of 1978 that I have on my Archive Extract and "1974" is, I think, due to there being a different number set for the Speedmasters at that time.
Thanks again.