Looks very much to me like the generic "one size fits most, sort of" holsters that were common in the United States in the first half of the 20th century.
I've seen many of these over the years, and have one that came with my Great Grandfather's H&R .32 Double Action breaktop.
These things were made, and sold, like M&Ms, and often accompanied one of the guns from the lesser manufacturers, H&R, Iver Johnson, etc., as a package deal.