This is a very odd duck.
Note the 37 dated Erma barrel. Also the ff suffix. They didn't make it that far in 41. Also 2 digit serials on some bolt parts, could have been post war refurb or certain depots or armourer repair possibly.
FF has nothing to do with year. Just serial suffix.
Can you post clear photos of any marking on the wood and on top of the receiver, and all waffenamts?