I am certainly no holster expert, but I have eyes <img border="0" title="" alt="[Eek!]" src="eek.gif" /> ... when compared with this excellent example of a genuine U.S. Test Holster that is displayed on Albert Beliard's website (I sure hope you don't mind Albert...
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the differences in design are very apparent...
Just look at the genuine belt loop (extends above the holster), the impression of the "US" Emblem and it's location, and the size and shape of the flap... reverse image or not... while it may be a similar design, I don't think this is a test holster either...
I agree that it is a revolver holster... probably for a Colt Army .38 caliber double action revolver...