Why Do Coins Have Ridges?

iStock/tweetyclaw
iStock/tweetyclaw

The stylish rims you might have noticed on U.S. dimes, quarters, half dollars and some dollar coins are called reeded edges. They’ve been on American currency almost since day one as a way of keeping people honest.

The United States Mint built its first minting facility in Philadelphia in 1792. The following March, it produced its first batch of circulating coins - 11,178 copper pennies. The silver coins that soon followed were linked to a silver standard, per the 1792 Mint and Coinage Act. This meant the “major” coins were at least partially made up of the precious metal (the first dollar coin, from 1794, was 89.25% silver and 10.75% copper). Silver dollars contained about a dollar’s worth of silver, give or take, and the others – half dollars, quarters and dimes – had a proportionate metallic content and size. Half-dollar coins contained ½ the amount of silver as a dollar and were half the size, quarters had ¼ the amount of silver, and so on.

Reeded edges served a two-fold security purpose for silver coins. One, they added an additional, intricate element to the coins that made them more difficult to counterfeit. Two, they prevented fraud.

How do ridges prevent fraud?

For as long as coins have been made from precious metal, a fairly common way to make a quick, ill-gotten buck was coin clipping. Clippers would shave off a tiny amount of metal all the way around the rims of a bunch of coins, collect the shavings, then sell them. Working carefully, a coin clipper could trim enough off of coins to make a nice profit, but not so much as to make them noticeably lighter or smaller. A clipper could then still go out and spend his devalued coins as if they were unaltered. Reeded edges ruined this scheme, since a shaved edge would be immediately obvious and alert anyone who received one that something was wrong.

Why don't nickels and pennies have reeded edges? Nickels and pennies are mainly composed of inexpensive metals, so the chances that they would be tampered with are low.

Before their adoption by the U.S. Mint, reeded edges were also used in the UK. When the physicist Isaac Newton became warden of the Royal Mint in 1696, he used reeded edges, among other means, to combat clippers and counterfeiters. Other European coins from as far back as the early 1500s also feature reeded edges.

Wait, are people still clipping coins?

Due to the abandonment of the silver standard and a worldwide silver shortage in the mid-20th century, the Coinage Act of 1965 authorized a change in the composition of dimes, quarters, and half-dollars, gradually shrinking their silver content down to the present-day 0%. Coin clipping is no longer a problem, but reeded edges are still around, a centuries-old security measure hanging on in an age where people pay for things with their smart phones instead of digging out pocket change. The tenacity is admirable. But why are they still there?

Coins are made by stamping coin blanks with a metal tool called a die. The die is engraved with the negative of a coin’s design, and the positive image is transferred to the coin when stamped. When the coins are struck, a part of the die called the collar holds the blank in place and applies the edge. When the silverless coins were first produced, the government didn’t see any need to make or buy expensive new dies or collars. Keeping the reeding wouldn’t hurt anyone, they figured, so the new coins were struck from the same old dies as the old ones, and reeding continued to be used as a matter of tradition and backwards-compatibility. Newer coins with updated designs (state quarters, new portraits) also have reeded edges. The design element lived to see another day on the new dies because reeding is useful for distinguishing coins by feel as well as appearance, making them more user-friendly for the visually impaired.

I can't stand the suspense. How many ridges are on my quarter?

If you gather up a bunch of coins, you'll see that not all reeded edges are created equal. The number and size of reeds on coins is not dictated by law, so individual U.S. Mints were long free to make their reeds to their own in-house specifications, leading to distinct style differences between coins from different mints and eras. Rare dimes from the now-defunct Carson City Mint’s 1871-74 runs, for example, have 89 broad, widely spaced reeds. The dimes made by the Philadelphia Mint in those same years have 113 thin, tightly-spaced reeds. 

Things are a little more standardized now and the Mint lists its reeding specifications as follows: dimes, 118; quarters, 119; half dollars, 150; dollar, 198; Susan B. Anthony dollar, 133.

Take Advantage of Amazon's Early Black Friday Deals on Tech, Kitchen Appliances, and More

Amazon
Amazon

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Even though Black Friday is still a few days away, Amazon is offering early deals on kitchen appliances, tech, video games, and plenty more. We will keep updating this page as sales come in, but for now, here are the best Amazon Black Friday sales to check out.

Kitchen

Instant Pot/Amazon

- Instant Pot Duo Plus 9-in-115 Quart Electric Pressure Cooker; $90 (save $40) 

- Le Creuset Enameled Cast Iron Signature Sauteuse 3.5 Quarts; $180 (save $120)

- KitchenAid KSMSFTA Sifter with Scale Attachment; $95 (save $75) 

- Keurig K-Mini Coffee Maker; $60 (save $20)

- Cuisinart Bread Maker; $88 (save $97)

- Anova Culinary Sous Vide Precision Cooker; $139 (save $60)

- Aicook Juicer Machine; $35 (save $15)

- JoyJolt Double Wall Insulated Espresso Mugs - Set of Two; $14 (save $10) 

- Longzon Silicone Stretch Lids - Set of 14; $13 (save $14)

HadinEEon Milk Frother; $37 (save $33)

Home Appliances

Roomba/Amazon

- iRobot Roomba 675 Robot Vacuum with Wi-Fi Connectivity; $179 (save $101)

- Fairywill Electric Toothbrush with Four Brush Heads; $19 (save $9)

- ASAKUKI 500ml Premium Essential Oil Diffuser; $22 (save $4)

- Facebook Portal Smart Video Calling 10 inch Touch Screen Display with Alexa; $129 (save $50)

- Bissell air320 Smart Air Purifier with HEPA and Carbon Filters; $280 (save $50)

Oscillating Quiet Cooling Fan Tower; $59 (save $31) 

TaoTronics PTC 1500W Fast Quiet Heating Ceramic Tower; $55 (save $10)

Vitamix 068051 FoodCycler 2 Liter Capacity; $300 (save $100)

AmazonBasics 8-Sheet Home Office Shredder; $33 (save $7)

Ring Video Doorbell; $70 (save $30) 

Video games

Sony

- Marvel's Spider-Man: Game of The Year Edition for PlayStation 4; $20 (save $20)

- Marvel's Avengers; $27 (save $33)

- Minecraft Dungeons Hero Edition for Nintendo Switch; $20 (save $10)

- The Last of Us Part II for PlayStation 4; $30 (save $30)

- LEGO Harry Potter: Collection; $15 (save $15)

- Ghost of Tsushima; $40 (save $20)

BioShock: The Collection; $20 (save $30)

The Sims 4; $20 (save $20)

God of War for PlayStation 4; $10 (save $10)

Days Gone for PlayStation 4; $20 (save $6)

Luigi's Mansion 3 for Nintendo Switch; $40 (save $20)

Computers and tablets

Microsoft/Amazon

- Apple MacBook Air 13 inches with 256 GB; $899 (save $100)

- New Apple MacBook Pro 16 inches with 512 GB; $2149 (save $250) 

- Samsung Chromebook 4 Chrome OS 11.6 inches with 32 GB; $210 (save $20) 

- Microsoft Surface Laptop 3 with 13.5 inch Touch-Screen; $1200 (save $400)

- Lenovo ThinkPad T490 Laptop; $889 (save $111)

- Amazon Fire HD 10 Tablet (64GB); $120 (save $70)

- Amazon Fire HD 10 Kids Edition Tablet (32 GB); $130 (save $70)

- Samsung Galaxy Tab A 8 inches with 32 GB; $100 (save $50)

Apple iPad Mini (64 GB); $379 (save $20)

- Apple iMac 27 inches with 256 GB; $1649 (save $150)

- Vankyo MatrixPad S2 Tablet; $120 (save $10)

Tech, gadgets, and TVs

Apple/Amazon

- Apple Watch Series 3 with GPS; $179 (save $20) 

- SAMSUNG 75-inch Class Crystal 4K Smart TV; $998 (save $200)

- Apple AirPods Pro; $169 (save $50)

- Nixplay 2K Smart Digital Picture Frame 9.7 Inch Silver; $238 (save $92)

- All-New Amazon Echo Dot with Clock and Alexa (4th Gen); $39 (save $21)

- MACTREM LED Ring Light 6" with Tripod Stand; $16 (save $3)

- Anker Soundcore Upgraded Bluetooth Speaker; $22 (save $8)

- Amazon Fire TV Stick with Alexa Voice Remote; $28 (save $12)

Canon EOS M50 Mirrorless Camera with EF-M 15-45mm Lens; $549 (save $100)

DR. J Professional HI-04 Mini Projector; $93 (save $37)

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How Much Is the Earth Worth?

The New York Public Library, Unsplash
The New York Public Library, Unsplash

Our home planet may be the most precious place we know, but it isn't priceless. The Earth's resources and the value it offers to humans add up to some unknown, tangible cost. The species may never have to worry about buying or selling the world, but thinking of it in terms of concrete numbers can help us better understand its value. Now, as Treehugger reports, one scientist has developed a special formula that allows us to do just that.

According to the calculations of Greg Laughlin, an assistant astronomy and astrophysics professor from the University of California, Santa Cruz, the Earth is worth roughly $5 quadrillion (or $5,000,000,000,000,000). He came up with that price after gauging the planet's mass, temperature, age, and other factors that directly correlate to its ability to sustain life.

To emphasize just how valuable the Earth is, Laughlin also estimated the worth of other planets in our solar system. Our nearest neighbor Mars costs about the same as a used car at $16,000. That's a fortune compared to Venus, which he appraised at the meager value of one cent.

Laughlin doesn't expect these numbers to have applications in the real world. Rather, he hopes they will inspire people to better appreciate the only home they know. He's not the first person to put a massive, hypothetical price tag on something just for fun. The cost of the Death Star from Star Wars has been calculated at $852 quadrillion—many times Laughlin's estimate for Earth.

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