What is a "strike through" error? Simply put, it is anything which is struck into the coin, but which was not "retained" in the strike. If the item was retained, it would be termed "struck through and retained (fill in the blank)." Coins have been found struck through buttons, wire, grease, plastic, tape, cloth, washers, sanding paper, other planchets, struck coins, foreign coins, fragments of other coins, springs, and numerous other things. It is a fascinating category of error coin collecting with lots of amazing coins within it. Where do all these things come from so that they can be struck into the coins? Well, the mint’s are factories, with lots of equipment made up of thousands of parts, machines dripping grease, bolts, screws, and random debris, and so there are lots of things which could break off, come loose, or accidentally be fed into a press striking coins.
One of the most important things in a strike through’s collectibility is if the item or substance struck into the coin can be identified. Most of the time this is easy, but it can also be difficult since things struck into the coin have a habit of getting badly distorted by the strike. If it cannot be determined, it falls into the most basic and uninteresting description "struck through", which means that the coin was struck through something, but what is unknown.
We will be discussing a small number of the different types of strike throughs in this article, as well as look at how to price and collect them. There are far more strike throughs out there than those listed here, but this is a good starting point, and these are some of the most often encountered strike throughs.
Struck Through Grease
This error type occurs when grease gets on the planchet or die and is struck into the coin. The grease can come from any number of sources including the minting press, which has lots of moving parts that get oiled, or it could come from the planchets themselves, which historically have at various periods in time been coated with a small amounts of oil. Coin’s struck through grease have a blurry image, as seen in the Louisiana quarter shown above. Sometimes the grease strike will partially obliterate the design, while at other times it will completely do so.
Grease strike throughs are very common for the most part, and only grease strikes which have obliterated large areas of the coin have any added value. The exception are coin series which are rarely found with errors of any kind. An example would be a 5 oz America the Beautiful coin, which is a series rarely found with any type of errors. But even for a coin like that, the strike through needs to be fairly large to really add much value. Because of how common grease strikes are (they’re probably the most common error type besides laminations), many times collectors who are doing date sets of errors will resort to using a grease strike coin for those super rare key dates. For example, if you where trying to get an error coin for every date and mint of Lincoln cent, you would likely have to get a struck through grease coin for the 1909-S VDB or the 1914-D.
This error type is often confused with die adjustment strikes. The difference between the two is that grease strikes will only be on the obverse or reverse, but will never effect the edge. Die adjustment strikes on the other hand always effect the edge as well as both the obverse and the reverse, with proportional weakness on the edge, obverse and reverse. They’re actually relatively easy error to tell apart once you realize this difference.
Struck Through Cloth
Far more rare than grease strikes, struck through cloth errors occur when a piece of cloth material is struck between the die and the coin, imprinting the cloth’s weave pattern into the coin’s surfaces. The cloth can come from a number of sources, but most likely it would come from a rag which was left behind by a mint employee who had used it for press maintenance. Quite rare on all series of coins, they are most desirable with a strong "weave pattern" in the struck through area. The weave pattern is the pattern of the threads in the cloth, and as can be seen in the Kennedy half dollar and the Lincoln cent show above, the weave pattern is easily seen. The weaker the weave pattern, the less desirable and valuable it is to collectors.
Most denominations of U.S. Coins are known struck through cloth, but the most to least common are: Lincoln cents, Jefferson nickels, Roosevelt dimes, Washington quarters, Kennedy half dollars, dollars. By far the rarest are Kennedy halves and dollars of which very few exist. Cloth strikes are valuable, and start around $200 for Lincoln cents, but can go as high as $2,000 for a nice example on a rare coin series such as dollars or half dollars. The two most important factors in desirability and value are how much cloth shows and how strong the weave pattern is.
Struck Through Feeder Finger
This error type occurs when a coin is struck through the feeder finger, which is the part of the press responsible for feeding the planchets between the dies. It is a short metal or plastic arm, which is made to be replaceable and of a soft material because they occasionally are struck by the dies, and the softer material keeps the dies from getting damaged. The strike through will take the shape of whatever the shape is of the feeder finger it is struck through. Above, see the feeder finger for the Chilean coin (which as a side note has also has been struck), and also the Chilean coin that was struck through a feeder finger. Note the straight and curved line in the struck through area on the coin, and how uniform the lines are. This is typically how coins struck through feeder fingers look.
Most collectors don’t add much value to a coin’s being struck through a feeder finger over a similar looking strike through (such as an planchet indent.) This is probably because of a lack of understanding by most collectors of just how much more rare coins are struck through feeder fingers, and also because they can be difficult to attribute as feeder finger strike throughs. This is an area for the astute collector to cherrypick and build a collection of rare coins for little money.
Struck Through Plastic
This error type is mostly found on bullion, and to a lesser degree on other modern mint products. Struck through plastic coins have a shiny, thin, even strike through which usually has a few straight lines and then is ragged elsewhere around the perimeter of the strike through. We know these coins are struck through fragments of plastic because many coins have been found with the plastic still retained in the strike through. The plastic comes from a covering which is used to protect the dies, and is removed prior to the die’s being put into service to strike coins. Sometimes not all the plastic is removed, resulting in a strike through. In the silver eagle show above, the coin strike through is very shiny (almost like the mirrored fields of a proof coin), and it is a classic example of a struck through plastic.
Struck Through Struck Fragment
This error type occurs when a struck piece of metal (often a fragment of planchet material) is struck, and then not ejected from the striking chamber. Another planchet is fed into the striking chamber to be struck, and then the fragment and the planchet are struck together. The fragment then falls out of the coin, leaving a small brockage. The above Washington quarter occurred in this way, with the fragment’s outline and the brockage visible on the quarter’s obverse. This error occurred when the struck fragment stuck to the obverse die after being struck, and then the quarter planchet was fed into the striking chamber and struck by the obverse die, impressing the fragment’s design as well as the quarter’s design into the planchet.
The error type is generally rare, and is known on most coin series. Values generally start at $100, and can go much higher into the thousands of dollars. The easier the brockage is to see, and the more wild looking the strike through, the more valuable and desirable it is.
Struck Through Dropped Filling
If grease and metal debris collect in any cavity of the die they can become hardened, and will take the shape of the cavity they are filling (imagine pouring hot lead into a mold, and when it hardens it is the shape of the mold—that is the principle at work here.) The grease and metal filling then falls out of the die cavity, and is struck into the coin’s surface. Often times, the filling will be from a letter or number since these small cavities are more susceptible to having debris become trapped in them. In the coin shown above, the state quarter had a die fill in the T of "LIBERTY." It fell out and was struck into the coin’s fields.
Most die fillings are worth between $50-$150, although depending on the eye appeal and rarity it could be worth more. They are generally rare, and a bargain compared to their rarity. Most error dealers do not have one in stock, and only get them from time to time. A collection of these would be very neat, and quite affordable since the collector would be limited in how much he could spend due to not being able to find many coins to buy!
Struck Through Struck Coin
A coin which has had another coin struck into it is called a "brockage." There are many variations and specific terms for the different kinds of brockages, but for brevity’s sake we will stick with the most basic definition. The above coin is a mirror brockage, which is a full impression of one side of a coin into the opposite side of the coin, giving in effect a "mirror image."
Brockages are known on all series and types of coins, and values range dramatically from a few dollars to thousands of dollars depending on the brockage type and the series of coin it is on. Do some research to find out values. Check auction process realized as well as what dealers are selling them for in order to get a feel for what the coins are worth.
Stuck Through Thread
This strike through occurs when a piece of string comes between the die and the planchet, and is struck into it. Often the string will be randomly spread across the planchet, and small fibers will be visible protruding from the struck through area. These fibers are tiny, and often can only been seen with a loupe. The coin show above is a Franklin half dollar which has had a thick piece of string struck into it’s reverse. There are many small fibers from the string, which can be seen with a loupe around the outer part of the struck through area. Without those small fiber strike throughs, it would be impossible to determine what precisely the coin was struck through. String can be different sizes, with some string being very thin, while other pieces are much thicker (such as the piece on this Franklin half.)
This error type is scarce, and is often found on proof coins as well as business strike coins. Why is uncertain, but doubtless is has something to do with the proof coin making process. The string may even come from the raggedy edge of a piece of cloth, with a string pulling loose from the rag and being the cause of a struck through string error. This would make sense on proof coins since the dies are frequently cleaned with a rag or other cotton material, which would make such an occurrence far more likely to happen than for business strike coins which do not often have their dies cleaned off.
In summary, there are lots of types and variations of strike throughs found on coins. They’re interesting and can be quite wild looking, and are fun to collect. A few collecting ideas would be to collect a particular type of strike through, such as coins struck through cloth, or coins struck through dropped fillings. Another option is to try to collect all manner of strike throughs for a particular design of coin. This would mean that the collector would look for a struck through string, cloth, dropped filling, etc for whatever coin series they collected. It would be challenging and quite fun as well.