"Die Tuba" ("The Tuba") is specialized in tubas made in St. Petersburg, Russia, managed by a German amateur player. The shopmaster stores the instruments in his house to sell the horns upgrading the valve linkages from poor Russian junks to cool German Mercedes.
The horn available at "Die Tuba" is of just one class: Large-bored Bb horn. The advantage of "Dir Tuba" is, after all, the price. A bare instrument as delivered from Russia costs only DM1,800, and the highest grade with German valve action DM4,050. In spite of the price, there are some very awful horns among the displayed tubas at Die Tuba.
Detailed story of St. Petersburg Tuba is found at "The story of St. Petersburg Tuba" in "Die Tuba" site.
I strongly recommend to visit the shop when you consider to buy an instrument from Die Tuba. Send a mail before visiting.