Mysterious French CC(?) Tuba in Berlioz Performance

[EPtuba]

I recently saw this recording of Bernstein conducting the Orchestre National de France in '73, and one of the tubas used is really throwing me for a loop.

link: https://www.youtube.com/watch?v=cao6WyF-61s

At about the 3:20 mark we get a nice shot of the tubists playing the Dies Irae. Already the tuba on the left is a bit odd, a 4+2 (or 3+2?) CC, but what really gets me is the silver horn on the right. It looks to be a top action 3+? CC Tuba, and it seems to me that he's using these fingerings:

F - 1
Eb - 3
D - some left hand valve (probably 5th)
C - open
Bb - 1

What exactly is this tuba? I have a thing for obscure horns but this really is something else. It's a top action CC which is already very strange. But on top of this, it has the traditional French long 3rd valve (same as modern 23). Also very odd that both tubists seem to be using the long whole step for D, considering the fact that the 5th partial is already quite flat. Regardless, seems like a one-of-a-kind build for sure, possibly custom built for French players making the switch from the "petit tuba" to a modern CC. After all, we do see that player switch to a traditional French C around 9:15. I'd love to hear everyone's thoughts on this - an ID on either horn would be much appreciated!

[Wilf.tuba]

I think the Tuba on the left might be an Alexander 168, same as the 163 but with the 3+2 valve setup. I have one and from what I can find out was made for French market.

The instrument in the right might be a Persy CC tuba like the one at the bottom of this page:

https://www.horn-u-copia.net/show.php?s ... 22Persy%22

I saw one once on eBay many moons ago, wish I bought it, certainly an interesting instrument!

[EPtuba]

That Persy CC sure looks like it'd be a blast to play! It's like what would happen if you took the petit C design and build a "legitimate" tuba with it. That 3rd valve slide does look ridiculously long though

[barry grrr-ero]

What impressed me is that while they were using two CC tubas in the upper octave, you could still hear the four bassoons in the lower octave. Those old French bassoons really cut.