Notice that hallmarks are optional on all products save watch cases:
“Currently all watch-cases in gold, silver, platinum or palladium, of foreign or local manufacture, sold in Switzerland, are subject to control and compulsory official marking.”Official controlling and hallmarking | Precious Metal Control | Swiss Federal Customs Administration
Current law has reduced the number of hallmarks to the single mark shown above — the head of a St. Bernhard dog. While not mandated in the law, the Office of Precious Metal Control files all refer to this St. Bernhard dog as “Barry.”
A single official hallmark will be used for all precious metals and all fineness standards, the “head of a St. Bernhard dog”:Official controlling and hallmarking | Precious Metal Control | Swiss Federal Customs Administration
While hallmarks are not required on other products, the Precious Metal Control still controls markings of “fineness” and “responsibility marks” which must adhere to applicable standards.
Note that for all our modern technology, the office still uses the “fire assay” method to determine the quality of the precious metal prior to hallmarking. The video below is instructive:
For information on historic hallmarks, please see Swiss Hallmarks 1880-1933 or Swiss Hallmarks 1933-1995.
Switzerland is a member of several the international conventions which bear on hallmarking. More information on those may be found at the International Hallmarking Convention (aka the 1972 Vienna Convention).
Generally speaking if an item bears the “Standard of fineness,” a “Responsibility mark,” the “Official hallmark,” and the “Common Control Mark,” then the item need not be re-certified in member states. An item exported from Switzerland to a member state would carry the marks seen below (with some exceptions for bi-lateral conventions).