Raised curving mound under motto 1990 lmc

Hi
Imho, @paddyman98 once said this is called a ridge-ring or
Design-Devouring Die Wear.

http://www.error-ref.com/?s=Ridge+ring

 

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Actually there are many instances that die wear on one die transfer to the other. One is called indirect die transfer. Or ghosting.

 

Ridge Ring. Very common on die deterioration. Can happen on any coin really.

There are actually 3 dies related to coin minting.
(a) the Anvil Die - the fixed one in the back/bottom.
(b) the Collar - the one that surrounds the edge
(c) the Hammer Die- the one slamming all day long.

The dies are not "synced" with each other. So they may go through 6 hammer dies for every 4 anvil dies. Dies tend to last from 1 to 3 days (though I don't know about how often collars are replaced) depending upon damage and how fast and long they use them, according to some math of how many produced and how many are minted per minute.

Ridge Rings, may occur on one or both sides. Depending upon each die's current state and whether the technician may replace one or both during a maintenance cycle.

Remember, non-Proof coins are made for commerce. They are made for money, not for quality. So they use the dies as much as possible to reduce the overall costs of manufacturing. They do not care the people oddly collect circulated coins. The Proof and Uncirculated sets are for collecting for them which they tend to use higher quality controls.