Hi Dirk, great find. Yes you are absolutely correct. Hallmarks of the French empire 1809-1819 and used March 1812 in today's northern Netherlands. Standard mark the French rooster 2 under his wing for .800 fineness, Office mark for departments, regional assay office letter S for department Frise todays present Friesland /Frisia province, assay office city of Leeuwarden. The crowned V is a later Dutch tax mark used 1814-1893, duty mark for foreign and other untaxed objects. See:http://www.925-1000.com/forum/viewtopic.php?f=5&t=32028
The maker's mark unfortunately is not clear. Could you try to make a few more images of the maker's mark?
The sifter is made before 1807 and probably made in Friesland and started of with a maker's mark only. Which is not unusual for 18th- early 19th century Frisian silver of a low standard or second standard below minimum .934/000 fineness. French hallmarking law of 1812 specifically states that all second-hand gold and silver objects, if not provided with valid marks, must also be assayed and marked to standard of fineness, or must be destroyed when below standard of fineness. This new law sent the sifter for re-inspection/re-assay in order it could be sold at an official shop/market or auction house.