[ithacaartist]

Yeah, my money's on a one-off. I notice it clamps to the pistol's stock lug, tightened by the knurled bolt on the toe of the holster in lieu of the familiar attaching iron. An interesting approach, since it solves the aesthetic problem of the 90 degree cross grain lid on those early, original wooden prototypes. And the clamp style attachment seems to me as if it would fit any stock lug without the need for fitting. Not sure about those reinforcing strips that are screwed on...

I would be cautious, however, of running afoul of the BATFE. IIRC, to be exempted from the SBR regulations, the stock has to be at least faithful to an original if it's a reproduction, and applied only to the pistol it would have been--1900/06, Carbine, Navy, Arty. Norwegian (?), etc.--in original, contemporary configuration.