Proofed in St. Etienne with powder T. Appears to be a nicely finished boxlock with sideclips and a crossbolt. Most likely short chambers at 65mm or about 2 1/2". If it is typical, it will have pretty tight bores and chokes.
It isn't worth a fortune. I'd bet it will work out to be a pretty nice shooter. Tell your customer to enjoy the gun and give him some coaching on lower pressure ammunition, in the correct length. We have a lot more access to it then we did 20 years ago.

Best,
Ted