Why do coins have ridges joke explained

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Last updated: April 8, 2026

Quick Answer: Coins have ridges, known as reeding, primarily as an anti-counterfeiting measure introduced in the 18th century. The U.S. Mint added reeding to gold and silver coins starting in the 1790s to prevent 'clipping,' where people shaved off precious metal edges. Modern coins like U.S. quarters and dimes feature 119 reeds, while half-dollars have 150. This physical feature helps visually impaired individuals distinguish denominations and aids in coin sorting machines.

Key Facts

Reeding was introduced as an anti-counterfeiting measure in the 18th century
The U.S. Mint began adding reeding to coins in the 1790s
U.S. quarters and dimes have 119 reeds each
U.S. half-dollars have 150 reeds
Reeding prevents 'clipping' where precious metal edges were shaved off

Overview

The ridges on coins, technically called reeding, have a practical history dating back to the 18th century when coins contained precious metals like gold and silver. Before modern minting techniques, people would shave small amounts of metal from coin edges—a practice called 'clipping'—to accumulate valuable material while still spending the now-lighter coins at face value. This became such a widespread problem that Sir Isaac Newton, while serving as Warden of the Royal Mint in 1696, helped develop solutions. The U.S. Mint adopted reeding for its first coinage in the 1790s, starting with silver dollars that featured lettered edges before transitioning to reeded edges. Today, while most coins no longer contain precious metals, the tradition continues with specific reed counts: U.S. dimes and quarters have 119 reeds, half-dollars have 150, and Susan B. Anthony dollars had 133. Other countries developed similar features, with British pound coins featuring milled edges since 1662.

How It Works

The reeding process occurs during minting when blank metal discs (planchets) are struck between two dies under immense pressure—up to 100 tons for modern coins. A collar die surrounds the planchet during striking, and when this collar has grooves, it impresses reeding onto the coin's edge. This creates raised ridges that are difficult to replicate precisely without expensive equipment, making counterfeiting more challenging. The specific number of reeds varies by denomination and country, serving as both a security feature and identification method. For example, the consistent 119 reeds on U.S. quarters and dimes helps automated sorting machines distinguish them from similar-sized tokens or foreign coins. The ridges also provide tactile differentiation for visually impaired users, as the edge texture varies between coin types. Modern minting technology allows for intricate edge designs beyond simple reeding, including interrupted reeding, lettering, and security grooves on higher-value coins.

Why It Matters

Coin reeding remains relevant today for multiple practical reasons. First, it continues to serve as a basic anti-counterfeiting measure, making it harder to produce convincing fake coins without specialized equipment. Second, the tactile ridges help visually impaired individuals distinguish between denominations—a crucial accessibility feature in currency design. Third, automated coin sorting and vending machines rely on consistent physical characteristics like reeding counts to accurately identify coins, with modern sorters using edge sensors to verify authenticity. Beyond functionality, reeding preserves historical continuity in coin design, maintaining a visual and tactile connection to centuries of monetary tradition. While digital payments increase, physical coins with these security features remain essential for transactions where electronic systems are impractical or unavailable, ensuring trust in everyday currency exchanges.