Can the single letter date codes stamped on Belgian firearms starting in 1922 be used as documentation for C&R status?

I'm trying to buy a gun from Cabelas with a 1941 date code, but they won't accept it unless I can document it in a book. I can't find it officially referenced in any book, and listings on the internet from folks like damascus-barrels.com isn't good enough for them. Does anyone know if these codes really count and where they're officially published?

Thanks,
Russ