M7 Auxiliary grenade cartridge redo

Found 3 of these “blanks” in a drawer of a gun shop I frequent. Pete D. may remember seeing these when he was there. Dimensions as follows;
OAL = 20.24mm / .797"
Rim dia. = 14.71mm / .581"
base dia. 12.10 mm / .476"
case mouth= 11.96mm / .471"
Rim thickness= 1.96mm / .076"
Red lacquered top wad, Case is magnetic, w/ a thin coating of what appears to be a lacquer. No apparent primer just a dimple in the base. If someone knows what it is, how was it fired/ignited? Heat? electric? Percussion?

if i remember is not a blank but aditional charge for propelling grenade rifle
i don’t know model number but it’s WW2 origine for use with garand for propelling various grenades by placing this charge in the grenade tail ,opening toward the barrel end
maybe used in korea war and vietnam but not sure

Thanks for helpful hint. Found this link on the site once I had an idea what to look for.