Show next to 12ga AAI grenade/action cartridge on left. I can get measurements, but appears to be some sort of 38spl blank. I have 2 of them, both read dyed heads, no headstamp, nice/unique crimp.
It is a heavy load blank for the Parker Ballistic Flarer, a cartridge-actuated tool for flaring tubes that was developed in the late 1950’s. There are also cartridges based on the .45 Colt case.