Standard boxlock (vs something like Darne/Charlin or maybe Manufrance Ideal), I'd get the stock work done in this country.

"Diamond steel" was used on quite a few French guns. It was the lowest quality steel described in the 1922 V-C catalog. In the 30's, describing their new "Helice 33" guns, V-C describes the basic model (#1) as having barrels "d'acier tres fin comprime" (very fine compressed steel), while the next higher model (#3) had "acier diamant" barrels.