Thanks for the info
I asked the same question on Swissrifle forum. Like you I thought the P37 was for privatising, but the person who replied to me on
there said that because there is a full stop (period) in between the P and 37, that this was not the case, but a armourers mark.
I havent seen any other examples of this on any other S-R rifle.

I would expect to see these marks on a Lee enfield or such

BLue