Hello and welcome to the forum.
Please see the following for French marks:
http://www.925-1000.com/Ffrench_marks.htmlThe guarantee mark disappears only in 1838. It was not a guarantee of the silver content of an object, but rather a guarantee that tax had been paid. It replaced the charge and discharge marks of the pre-revolutionary period. Therefore your object (flatware?) is appropriately marked for the time period.
Hope this helps to clarify.