I stumbled across this Bohemian firearms merchant but I can't say I have the name & location spelled correctly or that I know where in the world Kriegen(?) might be:
http://de.wikipedia.org/wiki/Kryry 
Looks like Gebhard Helmuthhauser or someone at the firm Carl Gottlieb Hänel made the tubes.
If that is an encircled "RS" and for Robert Schlegelmilch of Meiningen, it would have been some of his last effort as a barrel knitter as I think the shop closed in 1924.
Mass of tubes
Passed thru the Weipert facility in 1925
Sort of a swan's neck??
Kind Regards,
Raimey
rse
