There is a drop style holster on Ebay that the seller tells is associated with a Mauser 1910. You are welcome to take a look at it and express your take on this item. I enjoy drop holsters, but this one is new to me. After looking at it, I think it is a duty holster that has been modified. Perhaps 1950s vintage. That US car swivel style makes me think it is US manufactured for law enforcement duty.
Jim