Thanks Mike for the clue. That stamp reminds me of Krupp steel tubes made in Liege. Is the serial number in the 22k range? There weren't that many "N" craftsmen in the Suhl/Zella-Mehlis area with Adolf Niemeyer, a pistol maker being one, & the couple of Nordheim boys that I can recall right off.

Kind Regards,

Raimey
rse