Silver is a metal used for watch cases. Sterling silver is an alloy of 92.5% silver by weight, and the other 7.5% is mostly copper. Solid silver was once a common material for pocket watch cases. When wristwatches arrived, stainless steel and gold alloys largely took over. Silver is fairly soft and tarnishes easily.
Why does silver tarnish?
The dark tarnish on silver is silver sulfide. It forms slowly when the metal is exposed to sulfur compounds in the air. Tudor’s Black Bay Fifty-Eight 925 tries to deal with this. Its case is made from a silver alloy, and the brand keeps the exact make-up secret. The alloy is meant to answer worries about tarnishing.
How is silver purity measured?
Silver purity is given only in parts per thousand. Gold has a carat scale, but silver does not. Sterling silver is 925 parts per thousand, the same as 92.5%. Britannia silver is a higher standard, at 958. Coin silver is a lower grade, at .900 fine. It was widely used in United States coins made before 1964. So when a case is described as 925, the number shows directly how much of the metal is silver.
What does the lion passant mean?
In English hallmarking, the lion passant is the mark for the sterling standard. It guarantees a purity of at least 92.5% silver. It replaced the leopard’s head as the sterling purity mark in 1544. Testing silver goes back further still. In 1300 King Edward the First of England ordered that silver vessels be assayed before they left the maker. To assay is to test the metal for its purity.
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