J.B.:
Let me study on the pics but all seem to bear "CAL: 18?". And the way it has been worked off it makes me wonder if Sl(Belgian) make the tubes? I had thought those with the "CAL: 181" "S Bern" acquired the "CAL:181" in Bern, Switzerland but this example may offer more questions than answers. I'm pretty sure that it was P.O. Haggards of Sweden that has a 1894 Bastman catalogue which has a very similar model with a very similar safety. And it was Haggards noting the "CAL: 181 BERN" as a Swiss import mark. For now I can't say but maybe the "CAL: 18?" was already there?? Sometimes the load data is on the tube. But interesting too how the serial number and stamps associated with Sauer have also been worked off. Take XX,XX16, underside of the right tube and it should read "Imperial Eagle"(Eagle of Justice-Cate), "Caveman with staff", "CAL:18?", "S" or "Sl" and then "gKH"(all possibly script).
It sounds like Henry rifling but can you correlate it with any diagrams from his U.S. of A. patent:
http://www.google.com/patents?id=kU5rAAA...;q=&f=falseKind Regards,
Raimey
rse