Italian Military Rifle??????

I have a very old very crude bolt action rifle. Stamped Italy, 18, AT, and SG on the barrel where it threads into the receiver. Bottom of receiver stamped 7 :. In the receiver behind trigger mechanism is a star within a star. Magazine release is inside trigger guard in front of trigger. It does have a serial number, but no manufacturer. Waltnut military style stock with steel buttplate. and a very crude trigger mech. Any ideas on it's origin????