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.
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.
Compare the “R” in this photo to the “R” in the mechanical doubling photo above.
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
TEST Time #2: Doubled Die or Machine Doubling?
Another coin for your viewing pleasure. Is this 1998 Kennedy Half exhibiting a DDO, machine doubling or both?
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 ?
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
Thanks for the visit. If you have any questions about this coin, this website or other generic information about coins, feel free to drop us a note.
I can say this information was very educational for me. It has broadened my understanding of MD AND DDO’s..
Great job.
The hardest thing to comprehend for some is that machine doubling is going to be flat and shelf like. Doubled dies are stamped into the
die, and should be at the same height when a coin is made. to understand this better, I suggest taking some Playdoh or other material.
Take anything that has a design on it like a large medal or other oversized coin so you can see detail pretty good. choose a side of that
item to be pushed into the playdoh. I suggest using a suction cup to help remove the item from the playdoh so it does not damage the imprinted image.
Carefully reomve the item from the Playdoh. Now, we are going to put that item back into the playdoh, but turned slightly, like 5 degrees. Press it in as
hard as you did the first image. Remove the item. look at the images that were stamped into the Playdoh. That is basically the same routine the US Mint did to dies prior to 1990.
Each image is at the same height, or very close to it. The result is totally opposite from mechanical doubling. That classic cookie cutter line is actually one impression stamped over the top of another. Depending how close the mint workers were with the double dies, there very well may be some slivers of letters – almost at the same height.
Double dies typically will make the numbers and letters thicker. Machine doubling tends to damage the coin, making it shelf like and the numbers thinner.
These articles help alot but I guess it takes experience to spot the differences between doubled dies and strike doubling… Sure makes things interesting?
The hardest thing to comprehend for some is that machine doubling is going to be flat and shelf like. Doubled dies are stamped into the
die, and should be at the same height when a coin is made. to understand this better, I suggest taking some Playdoh or other material.
Take anything that has a design on it like a large medal or other oversized coin so you can see detail pretty good. choose a side of that
item to be pushed into the playdoh. I suggest using a suction cup to help remove the item from the playdoh so it does not damage the imprinted image.
Carefully reomve the item from the Playdoh. Now, we are going to put that item back into the playdoh, but turned slightly, like 5 degrees. Press it in as
hard as you did the first image. Remove the item. look at the images that were stamped into the Playdoh. That is basically the same routine the US Mint did to dies prior to 1990.
Each image is at the same height, or very close to it. The result is totally opposite from mechanical doubling. That classic cookie cutter line is actually one impression stamped over the top of another. Depending how close the mint workers were with the double dies, there very well may be some slivers of letters – almost at the same height.
Double dies typically will make the numbers and letters thicker. Machine doubling tends to damage the coin, making it shelf like and the numbers thinner.
then it becomes very difficult to differentiate a double dai unless it is the classic (1955)
Remember, Doubled dies are one impression on top of another, but slightly off. They are created with same pressure, so each impression should be at same height. Also the letters should show no damage. They doubled die is wider, the machine doubling usually looks thinner.
most important thing for doubled dies is most of the items are at the same height, and they ADD thickness to the coin. Machine doubling looks lower, shelf like and makes the the numbers and letters thinner.
I found this resource is very educational learning to identify either a coin is MD or DD. Thank you for making this happen.
You are welcome. Soon I will have more time to dedicate to educational posts. I appreciate the comment.
Okay, It makes sense.
If any error in the minting process ends up on the coin…we are just trying to determine what was the cause? If we know that, then we can understand the image on the coin…Hopefully. No matter if it is human error or machine error, if it is done during the minting process…would that not be called Mint Error? Why is machine doubling or damage not viewed as collectable or desirable? I’m new to this and am trying to understand why one is valued more than another.
Machine doubling and mechanical damage is so much more common. You can find literally thousands of machine doubling/mechanical damage to one doubled die. The damage was pretty evident in the 1950’s, 80’s and 1970’s.