Borchardt on Simpsons
 

Strange that in that condition, it would be missing the holster.

Not strange at all. A number of complete cased sets in as good or better condition have holsters that look pretty much like a brown rag. The holsters were made of a thin patent leather that did not hold up well, particularly if it was exposed to gun oil and/or not well cared for. Borchardt holsters are scarce and it is very rare to find an original Borchart holster in excellent condtion.