Hi
I think its armour piercing, buy I’m not that sure, the are a lot of markings on it, which are: on the base, 25 pr I.T. then P, J.2, LOT 1, 1.41, on the centre plug, there is, P7.IM, 3/4 O.R., with a W.D. Broad Arrow, then on the side: what looks like, HK, 6615, and a W.D. Broad Arrow. the centre plug screw in anticlockwise, leaving a hole?, what was the idea of this, any ideas.
Chunky