Found it in a 1983 S&W Leather catalog.
29 Slimline Holster
Comfortable and attractive, this body hugging holster is crafted from the finest leather,
accented by top stitching. Available fro small and medium frame revolvers with 2 to 4 inch barrels.
Features:
Body hugging style
Thumb break
Open muzzle
Favored F.B.I. tilt
1 3/4" belt slots
Size 44 is for Colt Trooper, Lawman, Official Police.
Your holster has a "tunnel" for the belt but the one shown in my catalog shows slots
similar to my Model 44 Hugger holster....Wrong photo in the catalog, or design change? Hard to say.
BTW My hugger holster is a size 34 for a 4" K Frame, but a K frame is a sloppy fit and a 4" N frame is about perfect.
KO