What explains the concave feature, seen along the edge moving towards the center of the coin? Did the US Mint use different a kind of die for commemoratives? Standard US coins seem to simply have a bold edge which then sharply sets a recess at about 90 degrees or so in towards the metal to allow room for the relief. Are there issues, inherent or otherwise, with this type of convex die that creates a concave surface on the coin? I think this concave recess is neat, especially when the words run along in relief of that banked, concave edge. It's the little things such as this that I like. Is it a signature of classic US coins, or are there examples of modern coins that follow this concave impression on the coin? I know there's the recent baseball and baseball glove commemorative that's ultra convex/concave, but what about standard issue business strike coins? Thanks in advance! Pic from the 'net:
The last coin that fits that description from the US mint is the 1987 Jefferson Nickel. The mint raised the relief and made it a bit concave like the original 1938 dated coin. Mid 1988 they went back to the spaghetti haired low relief garbage.
The 1926 Sesquitennial piece reminds me of medals, which sometimes have deep fields and high rims, high-relief designs, which the commemorative pieces were probably drawing upon. And how about cup-shaped Byzantine solidi... Why Did Byzantine Coins Become Cup-Shaped? [from CoinWeek.com 4/24/2015]
