I would fancy a better image of the monogram atop the tube but it appears to be >>KABA<< which was:
Karl Bauer & Compagnie. The concern was a Berlin based company with satellite offices in Breslau, Koenigsberg, Frankfurt am Main and Suhl. I would say the Suhl office was a sourcing point as Karl Bauer & Compagnie was not a Büchsenmacher, but rather a firearms merchant, wholesaler & a fierce competitor to GECO. Both concerns had their wares made on the backs of the talented mechanics in Suhl & Zella Sankt Blasii & Mehlis. Karl Bauer & Compagnie specialized in "Vogelbuechsen" and was active until the 2nd Major Disagreement in Europe.
Any images of the touchmarks? Being a Blitz platform, I would hazard a guess it was made in Zella Sankt Blasii - Mehlis.
Cheers,
Raimey
rse