A silver object that is to be sold commercially is, in most countries, stamped with one or more silver hallmarks indicating the purity of the silver, the mark of the manufacturer or silversmith, and other (optional) markings to indicate date of manufacture and additional information about the piece.
In some countries, the testing of silver objects and marking of purity is controlled by a national assayer's office.
Most of the time, you can find the answer simply by turning over the teaspoon, fish fork, ice cream saw, or cheese scoop (antique flatware is that specialized).
The French assay mark for sterling silver is the head of the goddess Minerva.
In England silver has been marked in some manner since the 12th century when it was first regulated by Parliament.
The marks made it possible to trace the maker and the place of manufacture.
The mark is a Lion Passant-the image of a lion walking, facing left.
You may be sure that an object bearing this mark is English sterling silver made after 1719.