Good stuff and thanks Doug!
'JJ' is Joseph Joiris of Nessonvaux who was a member of Syndicat des Fabricants de Canons de Fusil de la Vesdre.
I had not previously found a maker's mark on an "American Flag" tube so that is new information, and appreciated.
The gun is fairly late for a damascus gun; the L barrel 17.3 = .681" over 18.1 = .713" (muzzle constriction over bore 22 cm from the breech. 18.2 = .717" or 18.3 would be typical) was used after 1910. I suspect it is pre-WWI though. It does not carry Smokeless Powder proof, but that was not mandatory until 1924
