I also have a 4/4 one, but 'only' 5 valves in BBb. The valve section is conical from 18-21mm through the valve block. I believe it's a Model 102 or 103. It was popular in East Germany in the 70s for some reason with opera tubists. Mine for example was used in the Dresden Oper until the late 80s.
The information on the GDR B&S contrabass tubas is unfortunately a bit sketchy. I'll try and sum it up as much as possible, but some of the model numbers might be off.
B&S came to be in the mid 1960s, as the earlier name VEB was dropped. The VEB was a conglomerate of a number of earlier pre second war brass makers, but the main name to recognize is the company Hess. Hess started making brass instruments in the mid 1930s and in the tuba departement, they managed to head hunt the chief engineer from Alexander, who brought his notebook with him in 1935. Most of Hess's tubas look and play (in some cases, better) like Alexanders, ie. Models 163 or 164. After WW2 the company was closed and reorganized as VEB, who then continued the earlier Alexander like prewar designs. Then VEB becomes B&S, and again they continued with the earlier Hess designs with a few differences but obviously the same DNA.
Modell 101: the standard 4/4 B&S Bb tuba with 3 or 4 valves 19mm bore and a 42cm bell. The 1st and 4th valves are usually angled at 45 degrees entry to the valve block. A good solid tuba, with good intonation and easy to play.
Modell 102/103: upgraded version of the 101. Usually with a kranz and 5 valves, although sometimes cylindrical and other times conical with 6 or 4 valves. For some reason they tend to be made from a lighter gage brass than the 101s, but again is not 100% consistent. Most are from normal yellow brass, although a few goldbrass versions are floating around. These are awesome tubas, hands down. Like a BBb version of a Symphonie.
Modell 104: This is the B&S/Hess copy of the Alexander 164 Kaiser BBb with a 45cm bell. They generally were made for military windbands and a few orchester players. I believe the last one was made in the late 70s. They tend to have 2 bore sizes(always cylindrical), either 21mm or 22mm. There is a old story about the workers at B&S not having enough material to make the large bore blocks, so they 'acquired' some museum tubas, restored the blocks and used those on the new horns. Again not confirmed, but is a funny story...
Most have a kranz, some don't. Everyone I've seen has been yellow brass.
These are a mixed bag playing wise. Most I've tried tend to be a bit stuffy and out of tune, not exactly what one would expect from a kaiser tuba. However I recently tried one that was fantastic, every bit as good as a classic Alexander kaiser.
Again though, it's a rare bird, and I think even for communist times, there were better options available, but that's another thread subject.
Lastly, for the crazy projects. I acquired a Modell 102 with 3 valves in 19mm with a kranz, 'handmade' etc etc. I proceed to remove everything from the leadpipe to the dogleg and chucked everything in the bin. In went a 21.50mm 5 valve block with a new leadpipe, tuning slide and dogleg. It's currently in the hands of a collegue who is terrorizing his orchestra with it, but when it comes back later in the year, I'll post some photos and anyone in Berlin is more than welcome to give it a try.
Hope that explains a bit...
Best regards from Berlin,
TheBerlinerTuba
