As I understand British practice projectiles, were initially circa 1890 condemed service shell sometimes with the explosive charge and sometimes they were refilled with salt or similar to make the weight correct. Later and this is the question when did specific practice shot and shell start to be made? Certainly early 1940's sees solid iron 3pr, 3in and 12pr etc and filled shell for 2pr AA, these all have P stamped on the bodies. But when did the P start to get applied. The reason for the question began because looking at circa WWI 1.5pr and 2pr shell with and without tracer and with nose plugs fuze shaped, they are not marked P but what else could they be? Thoughts on this topic most welcome.