Blakesley Effect
The Blakesley Effect
Named after the American numismatist who first identified it, is a key indicator for authenticating a genuine clipped planchet error in coins. This effect is characterized by a noticeable weakness in the rim directly opposite the missing portion of a clipped planchet.
Explanation
The Blakesley Effect occurs due to the rimming process used to form coin planchets. During this process, a blank coin is rolled along its edge under high pressure between a roller and a fixed edge, which raises the rim of the coin. However, when the blank is incomplete—meaning it has a clipped portion—the pressure is relieved as the missing segment passes through the rimming machinery. As a result, the rim opposite the clipped area remains weak or unformed.
Identification
When such an incomplete planchet is struck to create a coin, the area opposite the clipped region will typically show a weakly struck rim. This is due to the absence of the raised rim, which would otherwise help in forming a well-defined edge during the striking process.
Example
A clear demonstration of the Blakesley Effect can be seen in coins that have gone through the rimming process and exhibit this characteristic weakness. This effect serves as a powerful tool for numismatists to identify genuine clipped planchet errors, distinguishing them from other types of coin damage or errors.
Important Considerations
- Rimming Process: The Blakesley Effect only occurs in coins that have undergone the rimming process.
- Authentication: This effect is one of the most reliable indicators for identifying authentic clipped planchet errors.
In summary, the Blakesley Effect is an essential concept in numismatics for the identification of genuine clipped planchet errors, providing insight into the coin minting process and the nature of specific coin errors.
