Tag Archives: Machine doubling

13 Common Mint Errors of Little Value

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Machines that make coins do so with tens of tons of pressure from incredibly high-speed mass production coining presses that use brittle steel dies on all manner of planchets, some with thin-plating zinc. As working dies reach the end of their lives, or as machines rattle from all that pressure, these common errors occur on different denominations (consult the Illustrated Glossary for definitions):

  • die chatter
  • die chips
  • die cracks
  • die gouge
  • delamination
  • die dent
  • die deterioration
  • filled mint marks
  • machine doubling
  • plating blisters
  • roller marks
  • split plating
  • struck through

These are only worth a few dollars, if you can find anyone who wants to buy them. Go to the “sold” button on eBay and you’ll see the results.

Here’s some die crack examples:

How, specifically, do these errors happen?

Die Deterioration, Chips, Cracks, Gouges, Die Chatter: These occur when working dies–minting hundreds of thousands of coins–become worn from the pressure and brittle. Minute pieces of the die break or crack from the pressure, and metal fill the voids with raised appearance.

Machine Doubling, Die Deterioration Doubling, Die Dents: These are mechanical errors as opposed to mint errors. They occur when the die bounces or moves during coining. The result is not raised but shelflike.

Filled Mintmarks: Until the late 1980s, mintmarks were punched directly into the working die. This was an extra step back then, so not only do the mintmarks appear in different places but also, depending on the punch, were susceptible to clogging.

Plating Blisters, Split Plating Doubling: After 1982, cents were made of zinc. these are caused by trapped gas or thin copper plating breaking over the zinc core, often mimicking doubling.

Roller Marks: Not technically an error, these resemble the mint error on cents called “woodies” (again, consult the glossary) that look like wood grain due to improper annealing. But roller lines are caused by uncleaned rollers used in the minting process.

Delamination: This happens a metal alloy does not cohere properly, resulting in the surface peeling off. These are common in older coins, especially zinc cents.

You do not need a coin microscope to see these. Magnification makes these common errors look significant; they are not. At best these sell for a few dollars on eBay.

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You can find more information about types, varieties, errors, grading, bidding and buying in Coin News Updated: The Essential Guide to Online Bidding. Please consider buying or gifting the work for a friend, as it underwrites this hobbyist blog. Thank you.

VIDEO: 3 Types of Doubling

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If you want a quick refresher of the major types of doubling–hub, machine and die deterioration–view this video. It will help you identify those types with audio explanations by Michael Bugeja.

Click here for an article on the 5 types of doubling.

Also, Proxiblog has assembled some 50 videos on this site and YouTube. Click the photo below to see them.

If you like posts like this, subscribe so you can be informed whenever there is a new article or column.

Proxiblog also has thousands of followers on Facebook Coin Groups, YouTube and other social media. To get the latest discussion and commentary, be sure to friend us by clicking here.

You can find more information about types, varieties, errors, grading, bidding and buying in Coin News Updated: The Essential Guide to Online Bidding. Please consider buying or gifting the work for a friend, as it underwrites this hobbyist blog. Thank you.

Machine v. Hub Doubling

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With the emphasis now on error coins, thanks in part to coin microscope sales and hyperbolic coin values on social media, it is important to know the difference between machine and hub doubling.

This is a tutorial.

Let’s start with a photo showing a machined v. hub doubled 1969-S cent. Both look significant. Only one is. Can you tell the difference? (We’ll return to these coins momentarily.)

Machine doubling, the above left photo, adds no or little value to coins. It happens when a die at the Mint begins to deteriorate and so may bounce during a strike, creating a flat shelf-like image. The date, device, lettering and mintmark can appear to be doubled.

Hub doubling, valuable, indicates a flaw in the die itself. Unlike machine doubling, which happens during a strike, someone at the Mint made an etching mistake. Mintmarks before 1989 were punched into the die; but this is distinct from hub doubling. We call these deviations “repunched mintmarks” (RPM). Hub doubling produces a raised, rounded impression that follows the flow of the date, lettering or device.

Let’s illustrate this again more closely with the 1969-S DDO cent, one of the most illusive coins, worth a bundle. It is ultra rare with PCGS holdering only 30+ coins. You can read about that here.

Clickbait social media says you can find one in pocket change. Oh, and you’ll need to buy a coin microscope for that. Fat chance.

New collectors who routinely consult social media for any number of topics often believe these hyped posts. Odds are you will never find a 1969-S DDO in rolls or pocket change. But you can find dozens of machined doubled ones on eBay and elsewhere masquerading as an authentic 1969-S DDO with sellers asking hundreds and thousands for a faux coin:

Let’s return to the images mentioned earlier and show distinctions between machine doubled and authentic doubled dies:

Machine Doubling, Left; Hub Doubling, Right

The machine doubled cent has a flat, shelf-like doubling. The doubling does not mirror the individual numbers but seem pushed to the right. The hub doubled cent has raised rounded digits that follow the contours of the numbers.

In addition to the ability to distinguish between machine and hub doubling, veteran collectors know how to identify replicas flooding the market from China. You can buy these fake ultra rarities on venues like Etsy for less than $30.

These replicas are purchased by scammers and then posted on eBay as the real deal. Now you have to compare devices with genuine coins. To do that, google a genuine one in a PCGS holder and compare doubled devices.

The obvious difference is the word “Liberty.” Take a closer look:

The doubling on the replica is mushy and below the original letters of “Liberty”; the doubling on the authentic coin is above “Liberty” with each letter mirroring the original and shifted to the right.

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Proxiblog also has thousands of followers on Facebook Coin Groups, YouTube and social media. To get the latest discussion and commentaries, click here.

You can find more information about errors and varieties as well as buying and bidding on coins in Coin News Updated: The Essential Guide to Online Bidding. Please consider purchasing the work for yourself or a friend, as it underwrites this hobbyist website. Thank you.