This is an Army Rifleman Marksman Sharpshooter pin from WWII, featuring a long rifle surrounded by oak leaf on a blue background. The back of the metal plate holds two clutch pins. The back says G.I. 1/20 S.I. Condition is very good, with slight flaking in the background. It is topped by a star, a feature most pins of this type do not have.
The sharpshooter medal can be yours for $45.