Nice try, Digby, but no. ;-)
I'm not attempting to prove anything. The statement was made about Gribeauval field guns not being produced after 1800. I found some photographic evidence that the Gribeauval System fortress and siege guns were being produced at least as late as 1810 and forwarded the idea that since that was taking place, perhaps Gribeauval field guns were still being produced.
I also asked for evidence. I do believe that is a reasonable request in a discussion of this type, don't you?
Now, where's the negative to prove? I don't believe I forwarded or proposed one.