The Roux is a big can of worms that has been opened as of late and info indicates that it was an advancement by a Jacques Roux of Belgium( http://www.littlegun.info/arme%20belge/artisans%20identifies%20q%20r/a%20roux%20jacques%20gb.htm ) on the Lefaucheux locking. The the Purdey twin underbolt was added but the name remained. So in short, one would have to a quite old single lockin underlever for it to be a true J. Roux action. Perhaps Axel will spin the yarn for us.

Kind Regards

Raimey