Tim,
The "Jallas & Cie" era catalog I have is a Cornell Pubs reproduction. My wife has a new scanner-I have an old computer. It hasn't been a good blend of tehnologies, otherwise what I have would be yours.
Not surprised to hear of the trouble with barrels you suffered, since, the old man (Paul) died, and took some pretty valuable skills with him.
A photo of the barrel flats would make grading possible, here.Francisque Darne was indeed Regis Darne's eldest son, and did start the company that built your gun. The designs were tinkerings of Regis Darne's 1894 patent guns to begin with, for the most part. Francisque Darne died in 1917, and the company soldiered on for many years afterward. I have a post 1945 catalog copy, and the guns all appear similar to the pre-war designs.
Much like many French (and other) companies in a tough market, the earlier, the better, but, not always.
I'll dig around and see what I can find.
Best,
Ted
