This cartridge was shown in the 1904 DWM catalog (as case #393) and would have been designed c1893 by DM-K. This is similar to the 9.5x57 Mannlicher-Schoenauer but was introduced much earlier and obviously available commercially for more than a decade.
I was unsure whether examples actually exist but because the DWM casebook shows a loading for this so I assumed that it is likely to have been produced.
Recently searching the Internet I discoved that an example appears to exist in the British Imperial War Museum collections:
Does anyone else have one of these or have seen this in the IWM collections ?
To me this is a great ‘find’ and I wonder if anyone from England can get a photograph of this cartridge and headstamp ?