French Double?

[cornelius]

A friend of mine has a 20ga sxs that we are trying to research to find some info on. There are not many markings on it. In a curved really stylistic script on the breech lever is "CYNEA'. 'St Etienne' is also under the barrels when you break it down. As well as '16.0' and a proof mark of 'PT' with a crown over. In my reasearch I found that the proof mark on the gun meant 'nitro proof', is this correct? Any help with the gun ID would be great. I've discovered that the proof mark and the St Etienne is french, is this correct? Is there any way to tell a manufacture or how old it is. Is it safe for even light powder loads?
thanks

 

[SDC]

Definitely French, but it's going to be hard to get a positive ID without some more information and/or a picture or two. If there are any more markings, they're likely to be on the top-rib, along the barrels, or engraved on the sides of the locks.