The gun on Littlegun has barrels by Joseph Cape, another Belgian maker. Defourny seems to have been involved with many other makers over the years. Marc can correct me if I am mistaken, but I believe he held several patents.
I have one listing that describes Brancquaert as "A maker of luxury guns". Apparently he never registered a trade mark. He is listed as being in operation circa 1905.
Another Brancquaert was sold by Christies.
http://www.christies.com/LotFinder/lot_details.aspx?intObjectID=5071941Pete
