sterling silver

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An alloy of 92.5 percent silver with copper or another metal.
• noun Objects made of this alloy.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An alloy containing not less than 92.5 percent of silver, the remainder usually being copper.
• noun Sterling-silver articles collectively.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a silver alloy with no more than 7.5% copper