Off-Centre Strike
Off-Centre Strike
An off-centre strike (or off-centre error) occurs when a planchet is not properly centred between the dies at the moment of striking. The design is impressed onto only part of the planchet, leaving a crescent of blank metal, and the coin emerges with part of its intended design missing. Off-centre strikes are among the most common and popular mint errors collected in Australia.
Explanation
Coinage dies are designed to strike a planchet that is held centrally by a retaining collar. If the planchet is fed into the press slightly astray - a mishap that becomes more likely as feed mechanisms run at several hundred strikes per minute - the dies close on it off target. The overlapping portion receives the design, while the unsupported crescent is simply squeezed flat, often showing a thin, stretched edge called the "blanks ear". The percentage of the design missing is conventionally used to describe the error: a "20 per cent off-centre" coin is missing a fifth of its design.
Identification
The unmistakable signature is the blank crescent of unstruck metal combined with a truncated design on the rest of the coin. The date and legends are often incomplete or absent, so attribution may depend on the denomination, metal and portrait visible. The planchet rim on the unstruck area is usually smooth and unworn, which distinguishes a genuine off-centre strike from a damaged coin that has been ground or cut down after leaving the mint.
Example
A typical Australian example is a five-cent or ten-cent coin struck perhaps 30 per cent off-centre, showing a partial echidna or lyrebird and a partial portrait, with a broad blank crescent opposite. Because small denominations are struck in enormous quantities, minor off-centre strikes of 5-10 per cent turn up in change with some regularity; dramatic misses of 50 per cent or more are far scarcer.
Important Considerations
- Degree: Collectors value off-centre strikes by how far off-centre they are - a 50 per cent or greater miss is a significant error, while a 5-10 per cent miss is modest.
- Completeness of date: An error that retains its full date and denomination is more desirable than one on which these details are lost.
- Authentication: The blank crescent must show original mint surface with no file marks, re-engraving or post-strike alteration.
In summary, an off-centre strike is the product of a mis-fed planchet caught only partially between the dies, and its combination of truncated design and virgin blank crescent makes it both easy to recognise and highly collectible.
