Silver Standards (Content) Explained . . .
Sterling means that the object is 92.5% silver or 925. This standard was established in England in 1300.  (At the time , this was the same as the coinage standard and thus enabled interchange of a silversmith’s work into coins or vice a versa as the economic situation, either personal or national, required.)
In England, this sterling content is assured by the presence of the lion passant or sterling lion hallmark.  In America, it is assured by the Sterling stamp.

French 950, 800, 925 - Before 1838, there were various marks that indicated fineness as well as where manufactured, in Paris or the Provinces. From 1838 to 1972,  French silver had two content levels: French 950 (95% silver) and French 800 (80%). The hallmark or poinçon de garantie for French 950 was the Minerve 1.

French 800 was guaranteed by the Minerve 2. The Minerve surrounds were the same but now a 2 appeared just below her chin.  Small 800 items were marked with a crab or warthog's head.
After 1972, France lowered the first standard of fineness to 925, the same as English and American sterling. The Minerve surround are the same, but a now block letter indicating decade of manufacture (e.g., A for 1973-1982) appears in front of her neck and the "1" appears at the back  of her neck.
Other countries have their own systems of hallmarking. Tardy International Hallmarks on Silver, available in paperback,  provides easy access to this information.
If a silver guarantee mark is missing it is easy to determine silver content yourself by using a chemical testing kit (available on the internet). When we feature an item that has no silver guarantee mark, we tell you what % the silver tested.  Also see Sheffield Plate