Clark was a known name in Holster making so I doubt they were affiliated with the Shoe Machinery Co. Since it shows some sign of being blackened at some time I had though it might be some private purchase thing. But why it would have been used with a 4"-6" revolver anytime since WW-I had me stumped. Holster does not seem large enough for a 1917. I can't find anything about dates of Clark holsters except it likely dates to before the mid-50s.
Anyway thanks everyone for the comments. Everyone else I have talked to about it seems to follow the private purchase idea as well. Which was what I figured. But when one is dealing with old gun stuff its wise to do some digging before concluding things.
Anyway I am going to tell the owner that is likely some private purchase thing. This does happen. I smuggled a Colt LW Commander to VN in my shaving kit and carried it in a X-15 shoulder holster.



So while neither were issue they were there carried by a Sp-4. Wish I had smuggled it home. But getting things back was harder than going over....