This confirms the information from the book that from 1964-1970 plus 1-2 yers the numberring system was changed to a letter-number combination eg 277 AH.
The present watch no serial number but the reference number that identifies it to the year 1963.
What's interesting is I have one of the watches shown AF / P 756D829 reference number, which means it was created before 1970 and particularly in 1969. I wrote about it on my forum:
http://www.pasjonaciczasu.pl/topic/440-36000-wahniec-na-godzine-10-ruchow-na-sekunde-5hz/?hl=36000
I'm sorry but it is in Polish. Maybe someone from the Polish reads and wants to explore their knowledge.
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