I purchased that horn, actually... The stamp on the bell says "Antoine Courtois, Paris, TU-410 C." I don't know if it was the only one Balt. Brass had, but that was the impression I got.
It's a great horn - big sound in proportion to size, very centered tone with good projection, great low register. Chris Olka (Seattle Symphony) played it and thought it was great - and he knows what he's talking about when it comes to equipment.
As for more, my understanding is that there wern't any (or at least many). It was made using B&S specifications in the Courtois factory as an experiment when they were both owned by the same corporation, which they no longer are. At least that is my understanding. I freely admit that I don't know much about equipment and the European instrument co.s goings-on, so I could be totally wrong. But this story is what I was told.
I know of another instance with a 606 copy made under the Accent label as a special request by an Accent artist. But again, I think this was a special situation, one-time thing.