Could you pleasure us with some pics of the underside of the tubes and on the forend? The marks might point toward sourcing of Suhl. I think the cartridge in the diagram is similar to C1 but I'll look for a listing. Kordell may have some insight.

Collath joined Teschner in 1859 and I would guess examples with Teschner only continued until the 1890s when Collath acquired the business. Collath sourced Mehlis for components to make this early Collath with the Teschner action:

http://www.littlegun.be/arme%20allemande/artisan%20c%20d/a%20collath%20w%20%20gb.htm

So with that I'd date your example from the 1880s and with just Georg Teschner's name atop points to the fact that Teschner was the wholesaler.

Kind Regards,

Raimey
rse