1965 Quarter Clip

Quote:
The Australian Coin Collecting Blog
The Blakesley Effect
Named after the American numismatist that first identified it, the Blakesley Effect can be the most powerful identifier of a genuine clipped planchet error. The effect is characterised by rim weakness directly opposite the missing portion of a clipped planchet error coin. This effect is a result of the rimming process that is used on most coin blanks to form a coin planchet. The rimming process rolls the coin blank along its edge under high pressure between a roller and a fixed edge, as it is rolled around the full circumference the edge is raised. When an incomplete blank rolls around this edging press the pressure is relieved when the missing portion contacts either the fixed edge or the rimming roller. The result is that no rim is formed opposite the missing portion of the coin blank.
When an incomplete coin planchet is struck the missing raised rim opposite the clipped region is typically very weakly struck simply because the rim is not raised. An excellent example of the Blakesley Effect is shown in Figure 2. It is important to realise that the Blakesley Effect will only be seen on coins that have been through the coin rimming process.