Why Do Coins Have Ridges?

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.

Big Questions
Why Is a Pineapple Called a Pineapple?

by James Hunt

Ask an English-speaking person whether they've heard of a pineapple, and you'll probably receive little more than a puzzled look. Surely, every schoolchild has heard of this distinctive tropical fruit—if not in its capacity as produce, then as a dessert ring, or smoothie ingredient, or essential component of a Hawaiian pizza.

But ask an English-speaking person if they've ever heard of the ananas fruit and you'll probably get similarly puzzled looks, but for the opposite reason. The average English speaker has no clue what an ananas is—even though it's the name given to the pineapple in almost every other major global language.

In Arabic, German, French, Dutch, Greek, Hebrew, Hindi, Swedish, Turkish—even in Latin and Esperanto—the pineapple is known as an ananas, give or take local variations in the alphabet and accents. In the languages where it isn't, it's often because the word has been imported from English, such as in the case of the Japanese パイナップル (painappuru) and the Welsh pinafel.

So how is it that English managed to pick the wrong side in this fight so spectacularly? Would not a pineapple, by any other name, taste as weird and tingly?

To figure out where things went wrong for English as a language, we have to go back and look at how Europeans first encountered the fruit in question, which is native to South America. It was first catalogued by Columbus's expedition to Guadeloupe in 1493, and they called it piña de Indes, meaning "pine of the Indians"—not because the plant resembled a pine tree (it doesn't) but because they thought the fruit looked like a pine cone (umm, ... it still doesn't. But you can sort of see it.)

Columbus was on a Spanish mission and, dutifully, the Spanish still use the shortened form piñas to describe the fruit. But almost every other European language (including Portuguese, Columbus's native tongue) decided to stick with the name given to the fruit by the indigenous Tupí people of South America: ananas, which means "excellent fruit."

According to etymological sources, the English word pineapple was first applied to the fruit in 1664, but that didn't end the great pineapple versus ananas debate. Even as late as the 19th century, there are examples of both forms in concurrent use within the English language; for example, in the title of Thomas Baldwin's Short Practical Directions For The Culture Of The Ananas; Or Pine Apple Plant, which was published in 1813.

So given that we knew what both words meant, why didn't English speakers just let go of this illogical and unhelpful linguistic distinction? The ultimate reason may be: We just think our own language is better than everyone else's.

You see, pineapple was already an English word before it was applied to the fruit. First used in 1398, it was originally used to describe what we now call pine cones. Hilariously, the term pine cones wasn't recorded until 1694, suggesting that the application of pineapple to the ananas fruit probably meant that people had to find an alternative to avoid confusion. And while ananas hung around on the periphery of the language for a time, when given a choice between using a local word and a foreign, imported one, the English went with the former so often that the latter essentially died out.

Of course, it's not too late to change our minds. If you want to ask for ananas the next time you order a pizza, give it a try (though we can't say what you'd up with as a result).

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at

Big Questions
Why Do They Build Oil Rigs in the Middle of the Ocean?

Ryan Carlyle:

We put the rigs where the oil is!

There aren’t any rigs in the “middle” of the ocean, but it is fairly common to find major oilfields over 150 km off the coast. This happens because:

  • Shallow seas often had the correct conditions for oil formation millions of years ago. Specifically, something like an algae bloom has to die and sink into oxygen-free conditions on the sea floor, then that organic material gets buried and converted to rock over geologic time.
  • The continental shelf downstream of a major river delta is a great place for deposition of loose, sandy sediments that make good oil reservoir rocks.

These two types of rock—organic-rich source rock and permeable reservoir rock—must be deposited in the correct order in the same place for there to be economically viable oil reservoirs. Sometimes, we find ancient shallow seas (or lakes) on dry land. Sometimes, we find them underneath modern seas. In that latter case, you get underwater oil and offshore oil rigs.

In the “middle” of the ocean, the seafloor is primarily basaltic crust generated by volcanic activity at the mid-ocean ridge. There’s no source of sufficient organic material for oil source rock or high-permeability sandstone for reservoir rock. So there is no oil. Which is fine, because the water is too deep to be very practical to drill on the sea floor anyway. (Possible, but not practical.)

This post originally appeared on Quora. Click here to view.


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