What is Quality of Strike?

February 14, 2009

If you're a coin collector and frequent internet coin forums then often you'll hear about a coin being 'well struck' or 'struck up' or 'having a good strike'. On the flip side you may hear of a coin 'having a weak strike', or 'not being struck up', or 'having a flat strike', or simply being 'poorly struck'. What exactly does this mean?

At it's most basic level when a coin is made or 'struck' a flat disk of metal is compressed between two dies with a great deal of pressure. The pressure is such that the metal moves to fill in the spaces or designs on the dies and the coin is formed. Milled coins use a third component of the coin called the collar to restrain the lateral metal movement of the coin blank and produce a coin of a uniform diameter. Sometimes the collar imparts a design on the edge of the coin, sometimes it does not.

When the metal of a coin blank fails to move sufficiently to fill in all of the design elements of the coin die then it is not fully struck, and some parts of the coin design will be poorly formed or even missing entirely. When the coin blank does fill the design elements fully and the coin truly reflects the intended design then it is well struck and fully formed. The reasons for poorly struck coins usually fall back to striking pressure and die wear. If striking pressure is too low then the coin will not be fully struck up. Striking pressure may be too low because the coin manufacturers wish to extend the life of the coin dies, or they may be lowered towards the end of a dies life to preserve it. When a die becomes worn it may even lose certain design features that simply wear off or are polished off during die maintenance. Technically coins struck from such worn dies are not neccesarily weakly struck, they are 'struck from worn dies'.

Weakly Struck Coins

The Australian Penny from 1953 to 1964 was struck with a portrait of Queen Elizabeth II of the United Kingdom. The ear of her portrait happens to be the high point of the obverse design and coincidentally is opposite a high point of the reverse design. This means that the metal movement required to fill the ear is quite large and the design feature is a good indicator of strength of strike. You can see in the image above the most weakly struck coin on the left progressing to the right with better struck coins. The ear is almost entirely missing on the first coin and is still not fully formed in the last coin.

Strongly Struck Coins

The image above shows much better struck coins. The coin on the left shows a fully struck up ear, but the design features are not completely sharp. The quality of strike improves to the right with the last coin being what I would call fully struck. It's a matter of conjecture with the last two coins as to which is better struck, and really it could be the quality of the photo that determines my judgement. However, the last coin shows more precise hair detail and overall sharper features and I believe it is the best struck coin.

I hope that explains what 'quality of strike' means!

Posted by mnemtsas at February 14, 2009 10:04 AM
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