Nightowl,
Until Dave gets back to you, I'll speculate that it is a "Tom Threepersons" holster by S. D. (Tio Sam) Meyers. Threepersons was a contemporary lawman. The holster is still available from El Paso Saddlery and possibly others. One caution, guns carried in a Threeperson's have a completely exposed trigger. That isn't considered "Kosher" today so be very careful carrying a doubleaction firearm in one.

Bob