Bob, good to know. If you ever need help with your consulting, that requires peeking at things in the US National Archives or Library of Congress, I'm not far from those. I've found a lot of old foreign publications in those places.
There's one I posted a couple of pages from, perhaps you are familiar with it, an 1880's periodical that had a 3-part series on the History of French Naval Cannons, I think it was maybe 200 pages in all. It is full of photos and tables. I suppose you already have photos of everything in the Invalides but the tabular data I've found nowhere else. I used it identify my French 4-pounder naval gun as a "probable Model 1779 4 pounder, short."