Geno, yeah you are correct on the firearms merchant. At a quick glance at many of the extensive images I guess it to be a Meffert Treff(coil springs), or variant, and not for the domestic German market per se. Meffert seemed to have a strong sourcing line to the Zella-Mehlis contingent of craftsmen for this Treff variant with the Roux type underlever. "SS"( with a punch mark) is very common on those as well as "GS" and for now I guess those initials to point to some of the Schilling klan. GGCA publication No. 41/Fall/Winter 2009 page 12 has a Chinaman's hammer Lefaucheux type dreiläufer peddled by C. Stiegele of München with the same stamp. I have little confidence that Stiegele applied much effort to the elaborate weapon. Their initials tend to have the over-strike on the "S" where the Sauer "S" or "S"s did not have that. Lower tube is from the Schilling forge and I would bet the pattern welded tubes were sourced from Liege as you indicate. Very interesting switcher/safety in the triggerbow guard as well as the stamp "Belgien 106297"??? I assume the selector is on the top tang?? I suspect the patent number on the top rib is for the pop up sight; note the lever in the doll's-head well in the receiver. Hopefully Axel or Shotgun Charlie has a reference on the patent numbers.
Kind Regards,
Raimey
rse