I noticed Heym makes medium calibre double rifles in the 8x75 mm RS chambering.

Has anyone ever seen a rifle or used a rifle in these chambering?

As a rimmed round it answers one of the criticisms of doubles chambered for such as the .300 Win Mag but with similar performance.

I believe it is based on the 9.3x74R case. Is this correct?

Any information and history of the round would be much appreciated. Thanks.