It should not be overlooked, that a good deal of know how was transferred from the US to B&M, when the latter produced US style instruments under the York Master name in the decades up to around 1970.
Actually I see no German traits with my own B&M made York Master BBb tuba (avatar). And I bought it from the US.
I am no following web auctions as intensely, as I used to do, so I cannot say for sure, whether there is B&M sousa up right now.
However there was one some 4 months ago. The seller alleged that it was a Conn copy. I am not too sure about that. Conn's tend to have fairly sharp stack and bell knees.
That BBb sousaphone can be seen at:
http://photos.groups.yahoo.com/group/yo ... saphone+3P
There is one major difference betwen US and European sousaphones:
In Europe they put slightly modified top-action-tuba-valve-sections on their sousaphones.
With at slight twist of RD (at least I think it was him):
In the US they put sousaphone valve sections on their front action tubas.
The US approach is by far the best from an airpath-efficiency viewpoint.
Really a bit strange, as the US makers basically took the efficient airpart from the Berlinen pumpen and improved it when applying the whole concept to piston valves.
I may document that later.
Klaus