I don't have much on "Pondevaux et Jussy". One of my book says that they were together in 1875 and that's about it.
I did find that Pondevaux was a (the?) director of the St-Etienne proof house in the late 1850s. So he was probably well respected.
The St-Etienne proof house was at the time a local affair,sponsored by the St-Etienne chamber of commerce. The Paris proof house was set up the same way in 1900 and actually operated in the beginning within the Bernard factory.
Dider Drevet was riding a bit on L.Bernard's coat-tails, as for marketing.
Bernard was the king of French barrel makers at the time and Drevet (among many others) was copying the type of marking that Bernard was using at the time. So it's pretty certain that the barrel set was made in 1885. The gun however could have been made immediately afterwards or, less likely, before, if the barrel set was a replacement. I sincerely doubt that in that case...
Best regards,
WC-
