Just as a quick glance, I think Monopol was registered to Auguste Francotte, so I'd look toward him as being the firearms merchant. I'd really like to see the stamp below the "67/49" stamp, which you have correct and that is the pre-rifling tube diameter. "S.S." might be for Sylvestr Schilling and possibly others. Any marks on the standing breech or near the forend hanger?

Kind Regards,

Raimey
rse