Am seeking help decoding stamps on a 2 inch mortar tail fin I uncovered, from a disused rifle range used for Australian troop training during WWII:
1st & 2nd pic: the 2 inch mortar tail fin (presuming HE), either side.
3rd pic: the base of the first tail fin of interest, nearest the base cap - reads as /|\ (broad arrow) over 13, with something possibly above the broad arrow but lost to the corrosion.
4th pic: same fin, with /|\ (broad arrow) over 64, again possibly something above the broad arrow but since corroded away. Below this where the tail fin screws on to the body of the mortar (so faint I couldn't photograph adequately), there is a /|\ over 24.
5th pic: the next tail fin, with BDC 6 42 Z stamped.
6th pic: the base-cap on this tail fin is still in place, with three circles surrounding the center of the cap filled with stamps - the photo is a little sketchy, but the top left circle contains the number 41 surrounded by strikes from the "6" position to the "1" position with 9 strikes in total (does this denote 9 months into 1941 as a build date - September??). The far right circle contains the figure "4", & the bottom left circle contains what looks like a "@" inside a smaller circle, or maybe a "9" inside two circles?
Any help massively appreciated!