My latest garage sale find is a projectile of a 75MM canon. Does anyone have any information, I have done an internet search and it is leaving me blank. It is 8" OAL, 2.940" diameter, the base has a 4" deep hole drilled into it that is 1 1/2" diameter with threads near the base. The markings on the base are “1942 GMC 75MM M61 S2 ???-22586”. I am assuming US manufacture, am I correct? The cavity in the bottom is too large and threaded to be used for a tracer element, in my opinion. Can anyone give any information as to the loading and use. Thank you as always.