It is a pretty nice looking gun. I would offer the distinct possibility that Robert Hubner bought a J P Sauer action and barrel set "in the white" and fit and finished it up and stocked it, adding his name as a small shop maker. The action clearly has an identical appearance to the Sauers of the period. The markings on the barrels are very blurred, but do I see an intertwined "SUS" in there?