This is a Uncle Mike's Shoulder Holster known as the Horizontal, model 7715-0.
For everyday wear" their Pro-Pak holsters are the ultimate. They're ergonomically designed" simple" lightweight and super tough. Pro-Pak holsters lie flat against your body" making them an excellent choice for use under jackets. They're constructed of an extra-thin laminate with a Kodra nylon outer shell. The smooth nylon lining protects your gun's finish and aids in drawing and reholstering.
Features:
Horizontal carry for a fast draw and lightweight comfort
Offside tie-down has single mag case for autos or single speedloader case for revolvers
Ambidextrous
Size 15
Fits 3 3/4 - 4 1/2 barrel large autos