Numismatic Coin Club World Internet Numismatic Society


Multiple Struck Error Coins
They Sometimes Escape the Mint
and End Up in Your Collection (Part 1 of 2)

By Ralph J. Huntzinger, WINS#158

We all know about the hammer and anvil dies.  But we sometimes overlook the collar die and its significance in the coin-striking process, especially as it relates to the production of error coins.  The collar is the third die in the coining chamber; a device which surrounds the edge of the planchet as the coin is struck.  The collar die keeps the coin metal from spreading larger than its intended diameter.  The collar die also imparts the edge design, if any, onto the struck coin.  The edge design includes such elements as the reeds, words, symbols or other edge devices.  Even the flat, smooth finishes on the edges of coins like cents and nickels are considered to be "edge designs" imparted by the collar die.  Multiple-struck error coins have a direct relationship to the collar die, and they come in two primary classifications:  Those struck more than once "within the collar", and those struck more than once "outside of the collar".

Multiple Strikes Within the Collar Die
Multiple strikes inside the collar fall within two realms:  intentional and unintentional.

In the intentional realm, there are proof coins and presentation pieces which are intentionally struck multiple times within the collar and usually have single, high-quality images.  The intent is to manually strike these coins multiple times to sharpen the quality of the design for collectors or for presentation purposes.  But things can go amiss even during controlled, manual striking.  If the "in-collar" coin happens to rotate between strikes (or, more likely, if a loose hammer die rotates slightly between strikes) then the struck coin may receive multiple, in-collar images.  The last of these multiple strikes will retain the sharpest image; with the images from the former strikes being mostly obliterated by each of the subsequent strikes.  And, though it's uncommon to find a proof coin with multiple, rotated images, it does happen.  Multiple images may also occur on proof coins if a loose hammer die doesn't rotate but, instead, it cants or shifts off-center.  This slightly-cocked die may impart multiple, overlapping images on a proof coin - usually one-sided.

In the unintentional realm, usually during the mass production of business strikes, when the ejector mechanism fails, an in-collar coin continues to receive additional strikes.  The striking pressure eventually causes the coin to begin to get thinner with the edges of the coin beginning to squeeze up and out of the collar die, forming a cup-shape or thimble-shape.  The sides of the cup- or thimble-shaped coin begin to form-up around the hammer die. The more strikes, the larger/taller the thimble-shaped coin becomes.  Some of these thimble-shaped coins actually, eventually adhere to the hammer die and become what is called a die cap.  This is what ultimately causes brockages and counter-brockages.

Multiple Strikes Outside of the Collar Die
When the coining chamber is functioning properly, a planchet is fed into the collar die, and on top of the anvil die, awaiting the strike of the hammer die.  (A planchet is slightly smaller in diameter than a struck coin, and it falls into the inner, circular recesses of the collar die.  The striking pressure expands the planchet into the sides of the collar die which forms the edges of the coin).  The thing to remember about "outside of the collar" strikes, is that the collar die "floats".  It's on a spring-loaded device which allows the collar die to recess around the anvil die and below the plain of the striking field within the coining chamber.  That's a fail-safe mechanism which keeps the collar die from being shattered when a planchet (or an already-struck coin for that matter) lands partially on top of it instead of into its center.  So, when a planchet is fed into the coining chamber and it falls partially off-center onto the top of collar die, the collar die, at the time of the strike, is depressed below the surface of the striking plain and isn't damaged by the force of the strike from the hammer die.  Once that off-center coin is ejected (and if the system goes on to work properly) the collar die springs back into place and is ready to accept the next properly fed/properly centered planchet.

Coins that are struck multiple times outside of the collar come in four primary classes:  1)Partial Collar Coins, 2)Planchets Which are Fed Off-Center, 3)Struck Coins Which are Re-Struck, and 4)Broadstrikes.

1) Partial Collar Coins
Remember that a struck coin is larger in diameter than its original planchet.  A partial collar coin is usually struck normally on the first strike and then either fails to fully eject from the collar die; or fails to fully eject from the coining chamber, causing it to bounce around in the coining chamber until it falls back onto the collar die in a centered fashion.  In either case, the subsequent strike of this coin forces the now-expanded coin partially back into the collar causing the portion of the coin above the collar to expand even further.  These strikes are sometimes referred to as "railroad rim" strikes because they resemble a train wheel with a protruding flange.

2) Planchets Which are Initially Fed Off-Center
The planchet falls partially onto the collar die, depresses the floating collar die below the field of the striking plain, and is struck once and ejected from the coining chamber.  This is what usually occurs to cause a single-strike, off-center coin.  But what happens if this off-center error fails to fully eject from the coining chamber?  It may continue to bounce around inside the chamber, landing again (and maybe again) partially onto the collar die, receiving additional, off-center strikes before it eventually fully ejects from the coining chamber.  You now have an error coin with multiple off-center strikes.

3) Struck Coins Which are Re-Struck
How about a coin which is properly/normally struck on the first strike, but fails to fully eject from the coining chamber?  It, too, may continue to bounce around inside the chamber, landing again (and maybe again) partially onto the collar die, receiving additional, off-center strikes before it eventually fully ejects from the coining chamber.  You now have a slightly different type of error coin which may be described as "first strike on-center, additional strikes off-center".

4) Broadstrikes
A broadstrike occurs when the collar die is stuck in the recessed position, usually due to a build up of grease and debris.  In this instance, when a planchet is fed into the coining chamber, fairly well centered, it can't fall into the confines of the collar die.  Instead, it rests on top of the anvil die with no collar in place to retain the strike.  Therefore, the planchet is struck between the anvil and hammer dies only.  This causes the coin's diameter to increase/spread.  Broadstrikes can occur as "centered" and "uncentered", meaning that the design elements are either well-centered or they're not.  What's the difference between an "uncentered broadstrike" and a "slightly off-center coin"?  Well, they were both struck outside of the collar, they both have an expanded shape, and they both look similar at first glance.  But the general rule of thumb is as follows:  If all of the coin's design elements are present (no design is running off the edge of the coin), then it's a broadstrike.  If any of the design is missing or running off the edge of the coin (no matter how slight) then it's an off-center coin.

Is it possible to have a multiple-struck broadstrike coin?  Yes it is.  The easiest manner for this to occur would be when a broadstrike coin fails to fully eject from the coining chamber.  It bounces around within the chamber, and falls between the dies again - usually off-center.  It may be struck one or more additional times.  This error coin might then be described as a multiple-strike broadstrike, the first strike being a centered broadstrike and the subsequent strike(s) being off-center.

Is it possible to have a multiple-strike broadstrike with all strikes being more or less on-center?  Yes.  The process might start with a centered-broadstrike coin which failed to eject from the coining chamber.  In this example, the collar die is stuck in the recessed position (probably clogged with grease and debris) AND the ejection mechanism is failing (the anvil die usually thrusts upward after a strike to eject the struck coin from the coining chamber - but sometimes the anvil die mechanism fails or also gets stuck or clogged with grease and debris and fails to push upward).  As a result, the broadstruck coin will remain seated on the anvil die and will continue to receive additional strikes from the hammer die.  Sometimes those additional strikes just cause the coin to spread slightly under the striking-pressure.  This spread affect can cause multiple, close-spread, overlapping images on the coin as well as some distortion to the coin's shape.  Other times, this free-standing broadstruck coin might move slightly on the anvil die between strikes due to vibration.  It will continue to receive multiple blows from the dies, causing close-spread, overlapping images as well as distortion of shape.  Eventually this error coin may eject from the chamber.

You must remember that this all happens in a flash!  Coins are struck on the older presses at the rate of about 2 per second per set of dies.  Many presses have up to 4 sets of dies operating simultaneously.  That's a lot of coins and blanks flying around in close proximity every second.

How do these odd-shaped errors get out of the Mint without being caught?  And how do they wind up in your collection?  That's the topic of part two of this article which is scheduled to appear in next month's WINS Newsletter.


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