I've never bought silver utensils before but I saw this one today and something about it called to me. I had to buy it. I was able to identify the maker and date - Francois-Dominique Naudin ca 1820 - but the back top of the handle has this mark (very large) and I can't find reference to it. Does anyone know what it signifies? Any help will be greatly appreciated.

http://www.collectingfool.com/spoon-mark.jpg
Thanks,
Ruben