This is a Uncle Mike's Shoulder Holster known as the Vertical, model 8301-1.
Superior weight distribution" along with ultra-snug firearm retention make their vertical shoulder holsters ideal for even the most active pursuits. The onside self-adjusting belt loop keeps holster close to your side and there is a fully adjustable shoulder harness with 2 1/2"-wide nylon web straps and a self-centering back-piece. These can be worn inside or outside your jacket. Fits up to 48" chest
Features:
Offside tie-down anchors harness to belt and lets you carry a speedloader or magazine case vertically or horizontally
Retention strap with combination adjustable buckle and snap keeps firearm in place
Right hand
Size 1
Fits 3 - 4 barrel medium autos and 3 1/4 - 3 3/4 barrel large autos