Pieper cape gun 12 and 9.3x57R (360 NE)? or maybe 9.3x60R?

I bought this gun as a 12 gauge and 38-55 combination. Pieper in fact made a 12/38-55 combination. 38-55 cases chamber. The prior owner believed it was a 38-55 and fired 38-55 from the rifled barrel. There is in fact a pair of stamps under the rifled barrel. One is ‘38’ and just after it ‘55’ While I am no expert there are a multitude of stamps which appear to be of Belgian origin, but none that designate the chambering that I can see.

Despite that – the bore is .366. 9.3x72R will not chamber – these cases are at least a half inch too long. I picked up some 360 Nitro Express cases as converted from 30-40 Krag by Buffalo Arms and loaded these with 9.3 diameter projectiles. They shoot very well and the fire formed cases appear to be straight walled. I am wondering if the length is correct. It might just be 9.3x60R if such a chambering was ever made.

Any chance that you have encountered something similar?

Thanks in advance for any info:

Mike