gold standard

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

• noun A monetary standard under which the basic unit of currency is equal in value to and exchangeable for a specified amount of gold.
• noun A model of excellence; a paragon.

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

• noun economics A monetary system where the value of circulating money is linked to the value of gold.
• noun idiomatic A test or measure of comparison that is considered ultimate or ideal.

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

• noun a monetary standard under which the basic unit of currency is defined by a stated quantity of gold
• noun a paragon of excellence