Why Do Coins Have Ridges on Their Edges?

Mark Adams

July 25, 2025

Key Takeaways:

Ridges, also known as reeds, were historically used to prevent people from shaving small amounts of metal off coin edges.
Modern-day coins have kept reeded edges because they help fight against counterfeiting, speed up machine sorting, and help people who are visually impaired.
The U.S. Mint and foreign mints cut edge designs during striking with a collar die, and each denomination has its own unique groove count.

All coins feel the same when they first touch your fingers, so the tiny ridges on quarters, dimes, and many other coins rarely get a second glance. In earlier times, money made of silver and gold carried full metal weight value, so shaving even a small amount from the outside edge could earn a small profit.

Ridges offer a quick visual cue that no metal has been removed from a coin. In this article, we’ll highlight the history of coin ridges, how they can protect against fraud, how they assist the visually impaired, how they are made, and how American Hartford Gold can help match you with a unique piece for your collection.

What Is the Origin of Coin Ridges?

Before nations relied on alloyed coins, most everyday currency circulated at or near its melt value. That practice brought with it both trust and temptation.

Coin Clipping

In medieval Europe, merchants weighed each incoming coin to ensure it was not tampered with. Street thieves quickly learned that a file or a sharp knife could skim thin curls of metal without damaging the design on the front or back. These shavings, when melted together, could yield a decent sum.

Buyers were slow to catch this because the original diameter still looked correct at a glance. The authorities tried implementing harsher penalties and heavier policing, but the low-risk, high-reward nature of clipping merely pushed the practice underground instead of eliminating it.

Coins lost nearly 20% of their intended weight after being out of production for a while. Economies slowed down each time these instances occurred, and traders began to demand payment in fresh, full-weight pieces only. Ridges offered a fix that no law could.

Mechanical Reeders

English engineer Peter Blondeau introduced an edge device in the mid-1600s, convincing the Royal Mint to adopt his screw-press technology. Instead of leaving edges smooth, Blondeau’s collar die pressed evenly spaced lines into soft metal during the same turn of the screw that struck the coin faces. The grooves acted as tamper-evident seals.

Recognizing his success, other European mints began to use similar machines, and the practice eventually crossed the Atlantic.

When the Coinage Act of 1792 created the U.S. Mint, officials equipped their new Philadelphia pressroom with edge-marking collar dies. A small engineering tweak solved a giant economic headache and set a global standard still alive today.

What To Know About Fraud Protection in the 21st Century

Today, paper currency relies on holograms and micro-text, and ridges team up with these design features to keep counterfeit coins out of pockets and everyday transactions.

Anti-Counterfeit Code

A skilled counterfeiter might duplicate a portrait on the face of a coin, but copying an unbroken circle with perfectly spaced grooves is much more difficult. Modern collar dies carve between 100 and 200 tiny lines on each quarter-sized blank. Every line has a precise width and depth, and any inconsistencies are revealed under magnification.

High-value bullion coins increase the level of difficulty for counterfeiters by adding edge lettering and hidden bevel variations that are visible only at specific angles. These micro-features require advanced tools that most counterfeit operations cannot afford.

Layering multiple edge elements allows designers to create a fingerprint that is nearly impossible to forge.

Change Verification

Coin handling machines rely on more than weight to sort change. Optical sensors scan the edge profile as each coin rolls past, confirming groove count and diameter. Reeded edges create a rhythmic reflection pattern that the machine reader translates into data points.

Speed matters in automated stations. Clear ridges allow software to reject bad coins in milliseconds, keeping lines moving and reducing maintenance calls. The small engineering decision made centuries ago now protects modern retail networks on a large scale.

What To Know About Ridges as a Sensory Tool

Security aside, ridges also serve as an inclusive design choice. Not everyone can see a coin’s color or print, so texture helps fill that gap.

People With Vision Loss

Slip a quarter and a nickel into your palm, close your eyes, and the difference is apparent. The quarter’s ridges stand out in comparison to the nickel’s smooth edge, indicating value even without visual confirmation.

For the millions of adults with low vision, that quick test prevents overpayment and encourages independence during everyday transactions.

The U.S. Bureau of Engraving and Printing only recently added tactile features to paper notes, but coins met this accessibility need long ago. While not officially considered a disability aid, reeded edges provide a valuable solution that supports individuals who rely heavily on their sense of touch.

International Currency

Other nations expand on this theme by including mixed edge types in a single denomination set. Canada’s two-dollar piece combines both smooth and reeded sectors, creating a unique notched feel. The European Central Bank encourages member states to select distinct edge patterns so travelers can tell euros apart when language barriers arise.

Japan’s 500 yen coin carries intermittent slanted grooves, while the United Kingdom’s one-pound coin carries alternating milled and grooved sections. Each coin type allows for easy tactile recognition, proving that edge mechanics remain fertile ground for inclusive design.

How Are Coin Ridges Made?

Crafting ridges may look simple, but the mechanics require a precision that exceeds even that of watchmaking. The smallest errors can cause jams, die fractures, or uneven wear.

Reeding During Striking

Blank metal discs, or planchets, first move through an upsetting mill that raises a thin rim around the edge. This raised lip centers the planchet inside the collar die. When the coining press closes, three components meet: the obverse die, the reverse die, and the hardened steel collar engraved with ridges.

Pressure exceeding 100 tons forces the metal sideways into the collar grooves while imagery sinks into the planchet surfaces. The one-step strike ensures perfect alignment between faces and edges.

Older screw presses required an extra pass for edge lettering, but modern-day presses can finish everything in a single stroke at speeds near 800 pieces per minute.

Different Coins, Different Grooves

Study a dime and a quarter side-by-side. A dime carries 118 reeds, while a quarter carries 119. That single-reed difference helps balance edge wear, mechanical stress, and symmetry relative to each coin’s circumference. Larger coins can have deeper grooves without risking splits, but smaller coins require narrower spacing to avoid defects.

Mints test prototype collar dies in simulations to study how alloy composition, die life, and expected circulation time interact with each other. The results are used to inform final reed counts and groove depths. Even small adjustments can affect something like vending-machine acceptance, so mints rarely alter coin specifications.

Acquire Something Unique With AHG

Coin ridges, at first glance, appear to be insignificant bumps, but they have protected the integrity of everyday commerce for centuries. They stump counterfeiters and give buyers peace of mind as they navigate day-to-day transactions.

At American Hartford Gold, we understand how important authenticity is, and we’ve been matching clients with quality pieces for years. From gold pieces for your Gold IRA to silver pieces for your collector’s display, we’ve got you covered. Reach out today to learn more.

FAQs

When did the U.S. start adding ridges to coins?

The U.S. Mint began reeding denominations like the half dollar and dollar in the late 1790s.

Why do pennies and nickels lack ridges?

Pennies and nickels contain only base metals, so they aren’t worth much. Omitting ridges on lower value coins speeds up production and leaves more time for higher value coins to undergo the reeding process, as those carry greater loss if targeted by counterfeiters.