The Answer Is Older Than You Think
Those tiny grooves running along the edge of a quarter or dime are called reeded edges—and they exist primarily to stop thieves.
Specifically, they were designed centuries ago to prevent a crime known as “coin clipping,” where people would shave precious metal off a coin’s edges and spend the coin at full face value.
Today, reeded edges still serve that anti-fraud purpose, but they’ve taken on a few other jobs along the way.
Pull a dime and a penny from your pocket and run your thumb along each edge. One feels like a tiny saw blade. The other is perfectly smooth.
That difference isn’t random—it’s the result of centuries of monetary history, criminal ingenuity, and one very famous scientist’s determination to fix a broken financial system.
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What Are Coin Ridges Called?
The ridges on the edge of a coin are officially called reeding (or a “reeded edge”). You’ll also hear them referred to as “milled edges,” particularly in the United Kingdom. The term comes from the minting process itself—a device called a collar die surrounds the blank coin during striking and imprints the pattern onto its edge.
According to the U.S. Mint, coin edges can be:
- Reeded – featuring uniform vertical grooves (dimes, quarters, half dollars)
- Plain/Smooth – no edge design (pennies, nickels)
- Lettered – with inscriptions stamped along the edge (some dollar coins)
- Decorated – with other ornamental edge patterns
The Real Reason Coins Have Ridges: Preventing Coin Clipping
Here’s where it gets interesting. For most of monetary history, coins were made of real precious metals—gold and silver. Their value wasn’t symbolic; it was literal. A silver coin was worth something because it contained a measurable amount of silver.
That created an obvious temptation.
Criminals would take a coin, file or shave a thin sliver of metal from its smooth edge, and then spend the coin as if nothing had happened. The coin looked almost identical. Most merchants wouldn’t notice. The criminal would repeat this across dozens or hundreds of coins, accumulate the shavings, melt them down, and sell the raw metal for profit.
This practice—coin clipping—was widespread and devastating. By the late 17th century, England’s entire financial system was in serious trouble. Silver coins in circulation had been clipped so many times that many contained far less metal than their face value implied. Faith in the currency collapsed. Riots broke out.
Isaac Newton’s Role in Fixing the Problem
This is where things take a surprising turn.
In 1696, the British government appointed Sir Isaac Newton as Warden of the Royal Mint—the institution responsible for producing England’s coinage. The role was traditionally ceremonial. Newton treated it like an engineering crisis.
At his disposal was a new minting technique: perfectly round, machine-made coins with intricate markings along their edges—letters, patterns, or uniform grooves. Newton used this to his advantage. When the government decided to recall all clipped and worn coins, Newton oversaw a massive recoinage program with remarkable efficiency. By the middle of 1698, the project was complete.
The result? Coins that were nearly impossible to clip without detection. The moment a criminal filed down the edge of a reeded coin, the uniform grooves disappeared—making the tampering immediately obvious to any merchant or banker who handled it.
Coin clipping stopped being profitable almost overnight.
Newton’s solution was elegant in its simplicity. The reeded edge wasn’t just a design choice. It was a tamper-evident seal baked into the coin itself.
Why Coins Still Have Ridges Today
Modern coins aren’t made of gold or silver. A U.S. quarter is mostly copper with a thin nickel cladding. Shaving it down wouldn’t yield anything worth stealing.
So why do we still add ridges?
As it turns out, reeded edges have proven useful in ways Newton never anticipated.
1. Anti-Counterfeiting Protection
Replicating a coin’s face design is difficult enough. Replicating the face and accurately reproducing the edge reeding adds a third layer of complexity for counterfeiters. The more difficult a coin is to fake, the less incentive there is to try.
2. Helping Visually Impaired People
This is one of the most practical modern uses of reeded edges. People who are blind or visually impaired can distinguish between coins by touch alone. A smooth-edged penny feels nothing like a reeded dime—even though the dime is actually smaller. Without those ridges, identifying coins by feel would be far more difficult.
3. Vending Machines and Coin Sorters
Modern vending machines and coin-sorting equipment don’t just weigh coins—they scan their size, weight, and edge profile. Reeding provides a consistent, machine-readable characteristic that helps automated systems verify a coin’s denomination and authenticity quickly and accurately.
4. Tradition and Continuity
When the U.S. transitioned away from silver coins in 1965, mints kept the reeded edges on dimes and quarters—partly because the edge designs were already embedded in the collar dies used during striking, and redesigning that tooling would have been expensive. Tradition played a role too. Reeded edges had become so associated with higher-value coins that removing them could have confused the public.
How Reeded Edges Are Actually Made
The ridges aren’t stamped onto a coin after the fact. They’re created during the striking process itself.
Here’s how it works:
- A blank metal disc (called a planchet) is punched from a sheet of metal.
- The planchet passes through an upsetting mill, which raises a small rim around its edge.
- The planchet is then placed between two dies inside a collar—a ring-shaped device that encircles the blank during striking.
- When the dies press together with enormous force, the metal flows outward into the grooves of the collar, imprinting the reeded pattern onto the edge.
- Every single ridge is created in one strike. It’s fast, precise, and consistent.
The collar die is the key innovation here. It’s what made Newton’s recoinage program possible in the 1690s and what continues to make reeded edges practical at scale today.
Which Coins Have Ridges—and Which Don’t?
Not all coins are reeded. In the U.S., the pattern follows a simple rule: higher-value coins get ridges; lower-value coins don’t. Historically, this made sense because precious-metal coins were the ones worth clipping. That logic has carried forward to modern coinage.
Here’s a quick breakdown of current U.S. coins:
| Coin | Edge Type | Approximate Number of Reeds |
|---|---|---|
| Penny (1¢) | Smooth | 0 |
| Nickel (5¢) | Smooth | 0 |
| Dime (10¢) | Reeded | ~118 |
| Quarter (25¢) | Reeded | ~119 |
| Half Dollar (50¢) | Reeded | ~150 |
| Dollar Coin | Lettered | N/A |
The dime is a particularly interesting case. It’s smaller than a nickel, yet worth more. Without the reeded edge providing a tactile difference, it would be easy to confuse the two by feel alone—especially for visually impaired individuals.
Frequently Asked Questions
When did reeded edges first appear on U.S. coins?
Reeded edges first appeared on U.S. coinage in the 1790s, on early half dimes, dimes, quarters, and gold coins struck in silver and gold. The early U.S. Mint applied reeding to precious-metal denominations specifically to deter edge clipping.
Why do pennies and nickels have smooth edges?
In the era of precious-metal coinage, low-value copper coins weren’t worth clipping—there simply wasn’t enough valuable metal to steal. That logic carried over to modern pennies and nickels. Since they contain no silver or gold, there’s no historical or practical reason to reed them.
Did Isaac Newton actually invent reeded edges?
Newton didn’t invent reeded edges from scratch—the concept of adding markings to coin edges existed before him. What Newton did was implement and enforce the practice at scale during the Great Recoinage of 1696–1698, making it the standard for British coinage and effectively ending the clipping crisis.
Are reeded edges still relevant as cash becomes less common?
Yes. As long as physical coins circulate, reeded edges continue to serve real functions—particularly for accessibility and automated machine identification. They’re also part of what makes coins difficult to counterfeit, which remains relevant regardless of how often people use cash.
Can you tell a coin is fake by checking its edges?
Sometimes. A missing or poorly formed reeded edge on a coin that should have one is a red flag. Counterfeit coins often get the faces right but fail to replicate the edge accurately. That said, detecting fakes usually requires checking weight, diameter, and composition as well.
A Small Feature With a Long History
Those tiny ridges on the edge of your coins have been doing quiet, important work for more than three centuries. They were born out of a monetary crisis, refined by one of history’s greatest scientific minds, and have since evolved to serve needs that Newton couldn’t have predicted—from helping blind people identify pocket change to telling a vending machine it’s looking at a genuine quarter.
The next time you hold a coin, run your thumb along its edge. What feels like a minor design detail is actually one of the oldest anti-fraud technologies in circulation.
