How does one manufacture a congressional gold medal?

U.S. Mint demonstrates the production process
By , Coin World
Published : 05/18/15
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The silver medals are 0.999 fine by weight; silver content is 298.701 grams, or 9.603 troy ounces. Gross weight is 299 grams, plus or minus 9 grams.

Bronze duplicates

The 3-inch and 1.5-inch bronze duplicate medals of the congressional gold medals are a copper alloy. The 3-inch medal is 89 to 91 percent copper, while the 1.5-inch medal is 94 to 96 percent copper.

The balance of the alloy for both sizes of bronzes medals includes lead, iron, phosphorous, zinc, and trace elements.

The 3-inch medals are struck vertically on a Sack and Kiesselback 1,000 ton hydraulic press. The 1.5-inch bronze medals are struck on a Gräbener Press.

For the 3-inch medals, the number of strikes and striking pressure varies depending upon the design. Medals with high relief require more strikes than those with little relief.

Most designs are struck two or three times and at tonnages varying from 400 to 550 tons. For the 1.5-inch medals, they are double struck with an average tonnage of 190 tons.

Traditionally, the obverse is the hammer die and the reverse is the anvil. However, occasionally a design will require the dies to be inverted for better medal flow, to solve metal fill issues, according to Mint officials.

The 3-inch gold medal blanks are provided by the West Point Mint ready to strike. The 3-inch silver blanks are provided by the Sunshine Mint ready to strike.

The 3-inch and 1.5-inch bronze blanks are provided by Olin Brass. The bronze blanks get upset to form raised rims and are burnished prior to striking.

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