Sterling, at 92.5 percent silver, is just one of the silver
standards in us today. Common standards include the following:
Coin Silver. This is a U.S. standard and is an
alloy of 90% silver and 10% copper.
Sterling Silver. This describes any allow that
contains at least 92.5% silver.
Mexican Silver. This standard from our friends
to the south is an allow of 95% silver and 5% other metal(s) -- usually
copper. (Most silver jewelry from Mexico is using the sterling
standard these days.)
Britannia Silver. Even more pure than Mexican
silver, Britannia silver has no less than 958.4 parts per 1000 silver, and
no more than 41.6 parts per 1000 of copper. Operationally, silver of
this quality is marked in the U.K. and Ireland as "958 silver."
Fine Silver. Most of us would rather have a
sterling reputation than a fine one, but in the world of silver, "fine
silver" is almost as good as it gets. Fine silver is 999 parts per
1000 of silver. This level of purity is found in bullion bars bought
for the underlying value of the silver, but fine silver is usually too soft
to be used in most applications.
The figure below shows graphically the differences among these
five standards. You may click on the image to see a larger version of it.