The #5 Jungle Carbine is a 1947. I would question the source of the wandering zero. I have shot a few of them and have seen sub MOA at 200 yards.
The No.1 Mk3 is a 1942 production from after the BSA factory was bombed in 1949. They were called Dispersal rifles because the the equipment was move to about forty smaller locations and seven primary assembly factories. Thia was along side of the #4 production at the same time.
Cheers
