Definition: A planchet is a prepared disc-shaped metal blank onto which the devices of a coin image are struck or pressed. The metal disc is called a blank until the time it passes through the upsetting machine which causes the rim to be raised. Once it has a rim, the disc is called a planchet.
Full article: https://pocketchangeriches.com/blog/2018/07/31/is-there-a-special-term-for-a-blank-coin-before-the-image-is-struck/
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