US Cartridge, 75mm Chemical, Mk 2
The Mark II shell design was an adaptation of the French M1900, and represented the older type of shell in use before the streamlined shape was developed. It had a copper rotating band, two grooves behind the rotating band for stab crimping of the cartridge case to the projectile, and a square base. The nose did not take the fuzes directly, but required an adapter that the booster was fitted to. The Mark II projectile varied from the HE Projectile MK I only in that it was pipe-threaded in the nose and had no base plate. (Absence of the base plate was common to chemical shells of all sizes.) The pipe threads in the nose of the shell insured a gastight seal in the joint between adapter-booster and the nose of the projectile.
Nothing else to see.