I don't think a target shooter would build up a sight ramp - many of us use home-loads, and it's simple just make a note of the sight setting to use at various distance. Also, there is an inspection mark, which means it is military. Question is: who was using obsolete ammo (Mks II - VI) after 1915? I reckon it was used in the colonies or something like that, where they had crates of old ammo for their troops to use up. After all, we regularly use 1930s dated .303 ammo today - I imagine that when the Mk VI - VII change happened, there were vast stocks of Mks II-VI ammo laying around.