What is machine doubling or mechanical damage?

machine doubling or mechanical damage

Why does machine doubling /mechanical damage occur?

Machine doubling or mechanical damage is worthless doubling. Machine doubling may occur when the minting press strikes a blank planchet and makes it a coin. Machine doubling is more than likely due to the configuration of the minting press, which is set up by humans. Add in the possibility of something going wrong in the striking chamber and an abnormal condition may be introduced to the machine as well. These all contribute towards machine doubling occurring. I visit coin forums and the number one issue that I see is that a vast majority of people cannot fathom what Machine doubling or mechanical damage is. How can one identify what machine doubling or mechanical damage is?

Machine doubling or mechanical damage happens a lot. Many people notice the machine doubling or mechanical damage but fail to correctly identify what this is. People tend to confuse machine doubling or mechanical damage with a form of hub doubling or doubled dies. They are worlds apart.

One has to realize that these are machines we are talking about and the setup is performed by mint workers who are human. Machine doubling or mechanical damage occurs when something within the actions of the machine cause an issue while it is striking the coin. Typically machine doubling or mechanical damage happens when the die is lifting after striking the coins but does not sufficiently clear the and the coin ends up taking some damage from this action.

How to identify machine doubling / mechanical damage on coins

I can show you thousands of photos depicting machine doubling or mechanical damage, but those photos aren’t the exact coin you may be holding in your hand. In order to quickly identify machine doubling or mechanical damage you need to focus on a few vital steps.

  • Machine doubling or mechanical damage can occur anywhere on a coin and on the obverse, reverse or both sides of the coin.
  • When a minting press strikes a coin and there is a slight misconfiguration on that machine, machine doubling or mechanical damage will more than likely occur.
  • When new dies are introduced to a minting press, the dies may operate extremely efficient and there may be no sign of machine doubling or mechanical damage.
  • Planchets or coin blanks are punched out of rolled metal sheets. These sheets can be slightly out of tolerance at times. When a specific setting on the minting press expects a specific thickness of a planchet and a planchet out of tolerance emerges, those planchets have the potential to receive an abnormal strike.
  • Over time, as these dies take on wear and tear, heat up and vibrate. The minting press be subjected by an event in the striking chamber which may cause a very slight setting to be introduced to the minting press, then machine doubling or mechanical damage may appear.
  • Over time the dies lose their luster and sharpness. This can aid in the die slightly slipping when the strike occurs. This condition is often called die deterioration and can be a contributor in producing coins that have machine doubling or mechanical damage. Always remember – this is a machine. Things happen.

How to identify machine doubling or mechanical damage

  • Machine doubling or mechanical damage is damage. It typically will damage some of the devices (letters, numbers and other items on the coin). For the letters and numbers one part of the letter of number can be at different heights. The KEY here is that if those two areas were put back together, they would probably look like one normal letter or number.
  • Machine doubling or mechanical damage will make the numbers thinner. It may change the surface color or have a different metal content showing.
  • Look for small tiny scrape lines where “shearing” may have occurred. If the die did not properly clear the coin and lifted at a very slight angle to the side, it may have sheared away part of the coin. These shearing micro-scratches in the area where the damage appears in a classic sign of damage.
machine doubling or mechanical damage
Machine doubling or mechanical damage shown on the letter “A”
Machine doubling or mechanical damage shown on the letter "R"
Machine doubling or mechanical damage shown on the letter “R”
Machine doubling or mechanical damage shown on the letter "S"
Machine doubling or mechanical damage shown on the letter “S”

Not a “new discovery” – more than likely it’s machine doubling or mechanical damage

People are some times critical when I ask them if the coin they have is listed on http://varietyvista.com or other coin attribution websites. They answer no, and I usually respond with then it is either machine doubling or mechanical damage. It’s my logical, almost safe bet approach.

Take a coin from the 1990’s. There were hundreds of millions if not billions of coins minted. Over 30 years has passed since 1990 and – this coin is just discovered by you, today? What are the odds? They are astronomical. The odds of finding a true “new discovery” on a coin that is over 30 years old is minute.

So how is a Doubled Die different?

For doubled dies, it is exactly what the phrase says. Let us travel to a time before 1995. The US mint used to take a master hub and place it at the top of a high tonnage press. Then they would take a new, blank working die and place it under the master hub. When the master hub is squeezed down onto the working die, they did not know if the image was sufficient. They had no idea if all of the details transferred successfully. In most cases, the mint workers would remove the working die from the press and inspect it. If it required an additional impression, it was placed back under the master hub.

IF the die was not correctly lined up, it it was placed under themaster hub too high, low or off axis, it would create a possibility that this working die could show the more than one impression. If the second or other multiple impressions were off enough, a doubled die was born.

The thing here to remember is that the doubled dies, the impression is sunk into the metal of that working die. This means there is a very good possibility that ALL the impressions should be at the same depth. Then when the dies are added to a minting press, the image is transferred to the coins it strikes, for the life of that die. The dies squeeze the planchet and the images that are sunken into the dies are raised onto the newly made coin.

Doubled dies tend to show a slight off-axis impression. This can be confirmed by seeing two images at the same heightand it may only show up in a certain area on the die. It’s vital to pay attention to how the researcher or attributer is showing the photos of documented doubled dies, because this area is THE area the doubling is seen and its struck in metal, so it does not move. Over the life if the die some of the area may be affected by the age but, it should be recognizable.

Doubled dies can show a cookie cutter style line when one impression is placed partially over the top of another. Doubled dies if slightly off access can show the tops or bottoms of the letters and number slightly doubled. This is usually referred to at “Notching” or “split serifs” when the letters have some separation. You might even see a “slice” of the letter or number… BUT it will be at nearly the same height !! It also ADDS thickness to the letter or number.

doubled die showing a classic cooikie cutter style line and split serifs. Compare the "R" in this photo to the "R" in the mechanical doubling photo above.
Doubled die showing a classic cookie cutter style line and split serifs.
Compare the “R” in this photo to the “R” in the mechanical doubling photo above.
A doubled die with E PLURIBUS UNUM showing doubling along with the classic cookie cutter lines
A doubled die with E PLURIBUS UNUM showing doubling along with the classic cookie cutter lines
A doubled die with E PLURIBUS UNUM showing doubling along with the classic cookie cutter lines
A doubled die with E PLURIBUS UNUM showing doubling along with the classic cookie cutter lines. Even the DOT is doubled !
Machine doubling or mechanical damage poster. Know the difference !
Machine doubling or mechanical damage poster. Know the difference !

TEST TIME ! Is this coin machine doubling or a doubled die?

The coin photographed below is a 1972-S Proof Roosevelt Dime. It is up to you to do the research on this coin and determine if the coin is displaying machine doubling or if this coin is an actual doubled die. Feel free to leave your comments down below this post.

Feel free to download these photos for the educational purposes only. They may show more devices on each photo.

OR

Simply RIGHT Click and choose “Open Image in a new tab” to view the full photograph online

The buster of dreams approach – Telling the truth educates the best

I was at the biggest coin convention in Fredericksburg, Virginia – The Virginia Numismatic Association (VNA). A friend and I just tag teamed together to identify a few coins that were not as claimed. My friend then told me a story about when he was at the Baltimore Whitman coin show and the infamous John Roberts was looking over a coin. John broke the bad news to the owner of the coin. The owners shoulders slumped and he sighed.

Then as the person left, John turned to my friend and said, “now you know why and what they call me – “the buster of dreams”. We aren’t proud of those moments, but that small thought prepares us to find a way to say the coin is not as expected.


Looking for more educational series? How about Struck on wrong thickness info ?

Ready for some more from the Educational Series?

Not a big fan of the educational series?  Take a look at our major mint error coins called Die Caps: Die Cap Major Mint Error Coins (minterrors.org)

Looking for “normal” coins? Please see Shop – US Coins, Silver Bullion and Numismatic products and services – TheCoinStore.org

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