1943 LB No 4 MkI* Question

I recently received my first British rifle, a 1943 LB No 4 MkI*. It appears to be original; no FTR or Import marks. I am wondering what significance the "10" stamped on the left side of the receiver may have and if any of you have seen any such markings before. There is a small C broad arrow marking on the Butt stock, I assume this signifies that the rifle stayed in Canadian service.

While your rifle is of British pedegree, it is a Canadian rifle, made at the Long Branch arsenal. The significance of the 10 on the left receiver wall is lost on me. I have seen some initials for Mounted Police, but never any numbers. Others may have a clue. The CA mark is found generally on later LB wood; the usual markings are the B over L stamp. Fine rifles.