The US Assay Commission was formed by the Mint Act of 1792 and continued to function until 1971, when precious metals were no longer used in American circulated coinage.
In 1977, no members were appointed to the commission. Then in 1980, President Jimmy Carter signed legislation to abolish the Assay Commission completely.
These 1981 Assay one ounce silver dollars have become rare American coins, not produced by the US Mint.
The Assay Commission's function was to supervise the annual testing of the gold, silver, and in its final year's base metal coins produced by the United States Mint to ensure that they met specifications. Beginning in 1797, it met in most years at the Philadelphia Mint.
In the late 1960s, the Defense Logistics Agency had over 165 million ounces of silver in its stockpile. The Federal Government sold much of this silver on the open market in 1980 and 1981.
After the US Mint stopped using silver in circulating coinage, the US government felt compelled to sell portions of its reserves to the public in order to stabilize the high silver market partially created by the Hunt brothers hoarding large quantities of silver.
The Continental Coin Company of California purchased a great deal of this silver from the U.S. government Treasury reserves. They proceeded to mint 1oz rounds, as well as 10 oz and 100 oz bars in 1981.
They made sure that everyone knew it was made from silver that had been stored at the San Francisco Assay Office by boldly stating MINTED FROM US STOCKPILE SILVER and Formerly Stored at US ASSAY OFFICE SAN FRANCISCO. Many people who buy these bullion products continue to think they were minted by the U.S. Mint in San Francisco for the Assay Office.
The CC on the reverse stands for Continental Coin rather than Carson City, further adding to the confusion. These bullion rounds are even represented by sellers as being minted by the US Government for the purpose of public distribution.
The obverse features an American Bald Eagle flying in front of the U.S. flag. The legend above the eagle says "One Troy Ounce 31.1 Grams" and the legend below says ".999 Fine Silver Trade Unit" with olive branches between the words around the rim. The design is reminiscent of US Mint coins, but not as detailed.
The center of the reverse states "Formerly Stored at U.S. Assay Office San Francisco" with the CC business logo beneath. The legend "Minted From U.S. Strategic Stockpile Silver" is around the border, and the date 1981 is flanked by 3 stars on each side.
These are only slightly more difficult to find than Engelhard Prospectors or other bullion silver rounds, but they aren't exactly rare American coins. They are an example of American precious metal bullion history that preceded the Prospector by a year.
The 10 oz and 100 oz silver bullion bars have similar details stamped in them, but aren't so easily confused for actual US Mint products. They look like standard bullion bars.