France has been over-run in not one, but, two world wars. On both occasions, guns that should have and would have seen good care, didn't. Petro chemicals of any nature were in short supply, and the guns that were retained by natives were often stored off site, so as to avoid prosecution if they were discoverd by the Hun or the later Nazis.
I've read of one shotgun that rode out both wars stored in a living tree. I'd expect it's condition reflects that.
Having a gun while occupied might have meant the difference between starvation and seeing the end of hostilities. Desperate circumstances seldom leave energy for the consideration of belongings and the associated maintenance. I've also read of loads for guns comprised of bits of glass, broken nails, or salvaged ball bearings.
If you needed a meal, you might not care what the specifics of the load you used were.
Speaking only for Darne produced guns, the specific steels used for production since about the mid 1930s were XT, for non magnum guns, and XTC, a French version of 4140, used for everything else. They are both very, very good gun steels, and I assume other makers were using something similar. The chrome content on XTC makes it difficult to blue. Both Stoeger and James Wayne offered a stainless steel barrel option on Darne guns in their catalogs, something I've never seen in person.
I've seen plenty of French and English guns with pitted bores. I've seen more English guns that had honing done to remove pits. I'm not sure honing benefits anyone but a seller, especially if he can convince a buyer that the bores look as they did when new.
Best,
Ted
