They are being polite
I would say the probably know exactly what the movement number refers to - and it is not the case reference you gave them. Or to be more precise they know what the reference written in the archive is. That is not always 100% correct. Mistakes have happened, people make errors in data entry. Even in the 1970's Switzerland.
There are times when the extracts are missing, or wrong, but when its a 31m serial I am confident in saying that the movement you have started life in a seamaster or devillle case.
Could have been in one of these - which you could not give away a few years ago - has a perfect calibre 861 inside.
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