The Assay Commission, made up of officials and presidentially appointed members of the public, tested relatively few coins, but had detected that some 1920-dated quarters struck at Denver were made of silver that was too pure, something missed by the Denver Mint in internal checks. See Mellon, p. 631. Mellon, Andrew W. (1922). Annual Report of the Secretary of the Treasury, 1922. Washington, DC: United States Government Printing Office.