Have no idea what is under the mount. My older brother purchased this rifle for $25 in the fifties. They were stacked on a table like cordwood at a store. This one caught his eye and purchased it. I traded a M1icon carbine for it which cost me a $125.00. Had it in the safe since then. I purchased a case of surplus ammo for it at $0.04 a round but never shot it. Maybe I will.