Die cap

In normal coin production, a blank piece of metal is placed between two dies, and pressure is applied to imprint the design onto the blank, creating a coin. However, sometimes a coin sticks to the upper die after being struck and is not ejected as it should be. When the next blank is fed into the press, the coin that is stuck to the upper die strikes the new blank. This stuck coin, now acting as a die itself, is called a “die cap.”
As the process continues, the die cap strikes more blanks, and with each strike, it begins to wrap around the upper die, gradually taking on a bottle cap shape. This deformation continues until the die cap is eventually removed, either through the automatic ejection mechanism failing to function properly or through manual intervention by mint personnel.
Die cap errors manifest in various forms, depending on several factors such as how long the cap stayed on the die, the material of the coin, and the force of the strikes. Here are some common scenarios:
Early Stage Die Cap: Initially, the coin may only show slight distortion, with one side having a normal appearance while the other starts to exhibit the wrapping or cupping effect. Details of the original strike may still be visible.
Mid-Stage Die Cap: As the die cap continues to strike additional blanks, it becomes more deformed. Coins struck by a mid-stage die cap may have a more pronounced cupping effect and may start to show blurring or doubling of details, as the die cap itself begins to wear and stretch.
Late Stage Die Cap: In its final stages, the die cap can resemble a deep cap or bottle cap shape. Coins produced by a late-stage die cap often have little to no detail on one side, with a smooth, dome-like appearance. The other side, struck by the anvil die, may retain sharper details.