No. 89Money3 minviews 29
Published by GK Library Annex
Why are there so many ridges around a coin?
Roll a 500-won coin between your fingers, and you can feel its jagged edge.
The vertical ridges around a coin were once added to stop people shaving a little metal off gold or silver coins. A break in the pattern made the damage obvious, making clipped coins harder to spend as if nothing had happened.
A trace of the days of coin clipping
Coins once held their value in the gold or silver they contained. Some people would shave small amounts from the edges, collect the shavings, and spend the clipped coin at its full face value. Regular vertical ridges made the shaved area visible at a glance.
In England, around 1662–1663 under Charles II, the Mint began making coins with ridges and lettering on their edges using machinery brought in by the French engineer Pierre Blondeau. The king's warrant states plainly that the aim was to prevent clipping and counterfeiting. Large silver coins carried the Latin words DECUS ET TUTAMEN, meaning “an ornament and a safeguard,” on their edges, and the same phrase later appeared on the edge of British one-pound coins.
Did Newton invent them?
A popular story says Isaac Newton invented coin ridges, but machine-edged coins existed about 30 years before Newton joined the Mint.
When Newton arrived at the Mint in 1696, a huge effort to recall all the clipped and worn old silver coins and replace them with new edged coins was already under way. Newton worked hard to make it run faster and more honestly, and he even tracked down counterfeiters himself and brought them to trial. He was less the man who created the ridges than the one who made sure those coins circulated properly.
Now a marker for your fingertips
Modern Korean coins are made from alloys rather than gold or silver, so there's little to gain by clipping them. Even so, according to the Bank of Korea, the 50-won coin has 109 ridges, the 100-won coin 110, and the 500-won coin 120, while the 10-won coin has a smooth edge. The ridges make counterfeiting harder and help you tell coins apart by touch in your pocket.
The United States is similar. U.S. Mint figures show 118 reeds on the dime and 119 on the quarter, while the cent and nickel are smooth, so you can tell them apart by size and edge without looking.
Related reads
The ridges around a coin are a trace of an old security pattern used to prevent clipping and theft of metal, rather than simply decoration.
Notes and references · Bank of Korea · Royal Mint Museum · U.S. Mint. Ridge counts follow the Bank of Korea's guide to circulating coins; machine minting in 1662–1663 follows the Royal Mint Museum and the UK National Archives; the warrant and Newton's role follow Oxford's ‘Newton and the Mint’; U.S. coins follow the U.S. Mint specifications. The Latin edge phrase is general numismatic history.
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