Multi-Strike (MST)
A multi-strike error occurs when a coin is struck two or more times by the dies. After the initial strike, the coin fails to eject properly from the press and receives one or more additional impressions. Each subsequent strike typically lands at a different position and rotation than the first, creating overlapping, superimposed design impressions that give the coin a distinctive doubled or ghosted appearance. Multi-strikes range from subtle double strikes with minor displacement to dramatic triple or quadruple strikes with widely separated design impressions.
A coin struck three or four times with significant offset between each strike displays a complex layering of overlapping designs that is immediately recognizable. Error-Ref illustrates an extreme case, a 1985 Argentine 10 pesos struck off-center at least 17 times.
How Does It Happen?
Modern U.S. Mint circulating-coin presses strike up to about 750 coins per minute. After each strike, the feeder mechanism ejects the finished coin and introduces a new planchet. Multi-strikes occur when the ejection step fails:
- First strike: The planchet is struck normally, receiving the full obverse and reverse design.
- Ejection failure: The struck coin does not leave the press. It may get caught on the collar or simply fail to clear the striking area before the next cycle begins; Error-Ref notes that the ejection failures behind multiple strikes are numerous and varied.
- Second strike: The dies close again with the already-struck coin still between them. If the coin has shifted or rotated from its original position, the second impression is offset from the first.
- Additional strikes: If the coin remains in the press, it receives third, fourth, or more strikes, each at a different position as the coin shifts between cycles.
Several factors determine the character of the multi-strike:
- Collar engagement: If the coin remains within the collar for subsequent strikes, the additional impressions are contained within the coin's normal diameter. If the collar is not engaged (or the coin has shifted partially out of the collar), subsequent strikes produce broadstruck or off-center additional impressions that expand beyond normal diameter.
- Displacement angle: The rotation between strikes determines how the overlapping designs interact. A 90-degree rotation produces impressions at right angles to each other. Error-Ref illustrates a 1998 Lincoln cent double struck in the collar with a 90-degree rotation between strikes.
- Offset distance: The lateral shift between strikes determines how far apart the design impressions are. Minimal offset produces a close double image; large offset produces widely separated, barely overlapping impressions.
The press does not know a coin is still in the striking chamber. It keeps cycling, closing the dies regardless of what is between them. Each successive strike flattens and distorts the previous design further.
How to Identify a Multi-Strike
Multi-strike errors display several diagnostic features:
- Overlapping design elements: Two or more distinct impressions of the same design are visible, offset from each other. On a double-struck Lincoln cent, you see two Lincoln portraits overlapping at different positions.
- Flat or distorted first strike: The first impression is typically flatter and less distinct because subsequent strikes partially obliterate it. The final strike shows the sharpest detail because nothing has struck on top of it.
- Different orientations: The overlapping designs are rotated relative to each other. Measuring the rotation angle between strikes helps characterize the error.
- Irregular shape: If subsequent strikes occurred outside the collar, the coin shows an irregular, non-circular outline where metal from later strikes expanded beyond the original coin's perimeter.
- Rim disruptions: Multiple strikes produce irregular, stepped, or flattened rims where overlapping strike zones meet.
Double Strike vs. Machine Doubling
Machine doubling takes several forms, and worn dies produce a look-alike of their own; Mechanical Doubling covers the whole family.
A common point of confusion is the difference between a genuine double strike and machine doubling (also called mechanical doubling or shelf doubling). They are fundamentally different:
| Feature | Double Strike (MST) | Machine Doubling |
|---|---|---|
| Cause | Two separate, complete press cycles | Die bounce, shift or drag during a single strike |
| Offset | Significant displacement (often several mm) | Slight and closely spaced |
| Design completeness | Two full, overlapping design impressions | Flat, shelf-like displacement of design elements |
| Detail quality | Both impressions show full relief | Doubled areas show flat, mushy secondary image |
Error-Ref attributes machine doubling to the die or press frame vibrating or moving during the strike. It happens within a single strike, while a genuine multi-strike is a separate press cycle.
Notable Examples
Double-Struck "Flipover" Coins
A flipover double strike occurs when the coin flips over between the first and second strike, so each face is struck the second time by the opposite die. The result is a coin that shows its obverse design struck over traces of the reverse on one side, and the reverse struck over traces of the obverse on the other. Error-Ref notes that flipovers are less common than multi-strikes on which each face keeps meeting the same die; it illustrates an in-collar flipover on a 1935 Lincoln cent.
Triple and Quadruple Strikes
Each additional strike represents another failure to eject, so coins struck three or more times turn up less often than double strikes. Triple-struck coins show three overlapping design impressions, and the visual complexity increases with each additional strike.
Double-Struck with Rotation
Double strikes where the second impression is rotated from the first produce two clearly separate design orientations on the same face. A related, less common case is a die that itself rotated between strikes: Error-Ref says this almost always involves the hammer die and is seen most often on proofs of the late 1960s and early 1970s, and it illustrates a 1966 business-strike nickel whose obverse die turned about 15 degrees between strikes.
Off-Center Multi-Strikes
Multi-strikes can combine off-center positioning with multiple impressions. A coin with a centered first strike and a 50% off-center second strike shows one complete design overlapped by a partial second impression extending off the edge of the coin.
Early U.S. Multi-Strikes
Double strikes exist on early American coinage, including large cents, half cents, and early silver denominations. The screw presses used in the early Mint's operation relied on human operators to position planchets and remove struck coins, so double strikes from failed manual ejection are documented from the Mint's earliest years.
Collecting Tips
- Count the strikes: Each additional strike leaves its own set of design elements. Counting the rims, dates or portraits present is the first step in describing a multi-strike.
- Offset and rotation matter: Double strikes with significant offset and clear rotation between impressions are the easiest to distinguish from machine doubling. Two clearly distinct, readable design impressions settle the question.
- Both strikes in the collar vs. one out: Note whether each strike was in the collar or out of it. A second strike outside the collar produces an off-center or broadstruck second impression and an irregular shape; Error-Ref files in-collar and out-of-collar multiple strikes separately.
- Date visibility: As with all strike errors, a legible date allows the coin to be attributed to a year; overlapping impressions sometimes obliterate it.
- Beware of fakes: Coins pressed together outside the Mint show incuse design transfer rather than direct die impressions, and they lack the sharp, raised detail of genuine strikes. Third-party grading from PCGS or NGC is strongly recommended.