The Guy Renne clarinet I have is a good example of a Couesnon clarinet. I have liked all of the Couesnon stencil hard rubber clarinets. However, this one has too many screws that refuse to budge, plus one broken key. I have elected to just keep it for odd parts.
Bore LH joint top: 14.85mm
Bore RH joint bottom: 14.85mm This is a little wider than some of their wooden instruments, and not as wide as the Jean Cartier, which could also be by Couesnon.
Clear signs of Couesnon being the maker are: