We need to see the right-hand side of the butt socket, under the bolt handle. You'll notice some considerable writing there. Most of what you're showing is proof marks, which are not very chatty, if you follow me.
That said, I do spy a "For Cordite Only" stamp, which tells me this is possibly a commercial No.1 Mk.III* made between the wars. The serrated trigger face would bear this hypothesis out, if it's not simple home-smithing. I would nearly bet this was a BSA made rifle.