I'm confident that a "CS" stamp as found on a tube is for the craftsman Caspar Schlegelmilch. I've seen it on German target arms as well. From the 1840s onward Caspar Schlegelmilch was a master tube maker along with Heinrich Schlegelmilch being a borer. Then during WWI Caspar Schlegelmilch is listed as a master/specialist barrel maker. So I'd say there were a couple of generations of Caspar Schlegelmilch. Now Carl Stiegele has "CS" but I think he was more of a firearms merchant and peddled the Vertikalblock Verschluss Heeren action: http://www.google.com/patents?id=BRtCAAA...p;q&f=false

Kind Regards,

Raimey
rse