yes, very unusual
was the very first time I have seen this gun but know this by seeing it in old catalogues. there is no other gun like this so you cant confound it.

quick search found another for sale in france and where they at home. I think it was a high quality double gun in its days.

http://www.naturabuy.fr/Fusil-Juxtapose-Manufrance-Ideal-Lunettes-Canon-Damas-item-1825337.html
12 ga with damscus steel barrels, 1700 euro for an old gun is a fresh start but its possible the real value - nitro proof?

if they ever build double rifles with this action?