It has parts of a genuine no4 T (butt stock, etc) but other things are worrying. The number stamping is shonky and not similar to any military numbering I have seen. The mount may well be an original but has recently been fitted to the that rifle, as is evident from the recent file/sanding marks, restruck screw staking, heat/cold blue marks, etc. I would say it is assembled from an original No4 T rifle (without the original mount) and has recently been set up with another mount and renumbered.