PART VI. Striking Errors:
Multiple strikes:
In-collar/out–of-collar
Definition: Multiple strikes can occur inside the collar or outside the collar.
A 1998 Lincoln cent double struck in-collar with 90 degree rotation between strikes.
Definition: Multiple strikes can occur inside the collar or outside the collar.
A 1998 Lincoln cent double struck in-collar with 90 degree rotation between strikes.
Definition: Multiple strikes can be either on-center or off-center. The reasons for multiple strikes are as varied as the number of strikes that can occur. Ejection failures which prevent a planchet to correctly discharge from the striking chamber are numerous.
A 1985 10 pesos from Argentina which has been struck off-center a minimum of 17 times. This coin was highly distorted by several other planchets entering the striking chamber. Complete details of each strike were obliterated by these intruding planchets.
Definition: The presence of two or more misaligned strikes on the same face of the same coin. The position of the affected die can be stable or quite unstable.
It is rare for a coin to be struck more than once by a misaligned die. It is even rarer for those strikes to be well-separated as the result of die instability. This undated India 10 rupees coin (2019 – present) features a 31% off-center first strike and a series of at least six additional off-center strikes that were all 79% off-center. The hammer die was properly centered during the first strike. However, during the later off-center strikes, the hammer (obverse) die became progressively more misaligned until it finally migrated beyond the coin. The coin showed very little movement during those later strikes and the anvil die remained fixed in position.
Definition: This error occurs when a newly-struck coin fails to properly eject from the striking chamber and is struck several more times by the same die pair. A multi-struck error of this nature can occur inside or outside of the collar.
This 2000P Sacagawea dollar coin was struck 6 times. The first strike appeared to be normal, while the remaining five strikes were delivered off-center. The coin moved slightly between each off-center strike.
Images are courtesy of Heritage Auctions.
Definition: Most multi-strikes show the same face struck repeatedly. Coins that flip over between strikes are rarer.
The 1935 Lincoln cent shown below is an in-collar, flipover double strike. After a normal first strike, the coin flipped over and landed back inside the collar. It was then struck a second time.
The 2000 Lincoln cent shown below was first struck off-center. It then flipped over and was struck a second time
even farther off-center. The second strike is uniface (struck against another planchet).
Definition: After a centered first strike, the hammer dies tilts down at one pole and strikes the coin a second time at an angle. The result is that one pole is extremely well-struck on both faces while the opposite pole shows little or no trace of the second strike.
The illustrated 1976 Israel Greeting medal was minted by the Israel Government Coins and Medals Corporation, a quasi-public entity that produces all of Israel’s coins and medals. The first strike was quite weak, but was centered. The second strike was delivered at an angle of approximately 45 degrees.
This medal shows both a vertical misalignment (tilted die error) and a 50% horizontal misalignment of the hammer die. The hammer die started shifting position immediately after reaching the lowest point of its downstroke during the first strike. As a result, newly-struck letters in the northwest quadrant were badly scraped.
Vertical misalignments of greater than 15 degrees are almost always accompanied by a horizontal misalignment. This is because when a die tilts down at one pole, it also swings in, unless there is compensatory lateral movement of the die or die assembly in the opposite direction.
Definition: This error occurs when the coin is struck at least twice with one of those strikes showing a rotation of either the hammer or the anvil die.
On rare occasions a double-struck coin will show that one of the dies (almost always the hammer die) rotated between strikes. Such errors are most common on proofs from the late 1960’s and early 1970’s. This 1966 nickel shows a rare business strike with such an error. The hammer (obverse) die rotated about 15 degrees between the
first and second strike. This coin comes courtesy of Thomas Barosko.
Definition: This error occurs when a coin is struck at least twice and the subsequently strikes shows an offset in direction.
A horizontal, vertical, pivoted, or rotational misalignment can occur on the second strike after a normal first strike. It’s also possible for a misaligned die strike to precede a normal second strike, although this has only indirectly been documented through clash marks.
In this 1999 cent, the hammer (obverse) die was centered during the first strike. Between the first and second strike, it shifted to the right about 10%. Before the hammer die descended a second time, an unstruck planchet intruded into the striking chamber, leaving an indent on the left side. Details of the first strike can be seen in the floor of the indent. The second strike also shows a partial collar error
Unstruck blank (“Type I”)
Unstruck planchet (“Type II”)
Die alignment errors
Collar alignment errors
Collar deployment errors
Weak Strikes (ES Sept/Oct 2000; CW 5/3/04, 9/11/06, 6/18/07, 3/1/10, 5/23/11, 6/23/14, 8/27/18, 3/2/20, 10/26/20, 11/27/23)
Skidding Coin Errors (CW 1/29/18)
Abnormally Strong Strikes
Stutter Strikes (ES Nov/Dec 2001, Sept/Oct 2007; CW 12/28/09, 7/25/11, 8/10/20)
Concentric strike lines generated by a single strike (ES Jan/Feb 2012; CW 12/26/11)
Machine doubling (a.k.a. machine doubling, machine doubling damage, machine damage doubling, mechanical doubling, strike doubling, shift doubling, ejection doubling) (ES July/Aug 2006; CW 3/15/10, 7/24/17, 12/23/19, 3/30/20)
Rim-restricted design duplication (form of machine doubling) (CW 10/6/03, 2/22/10, 5/24/10, 12/6/10, 5/13/13, 12/30/13, 3/8/21, 4/12/21)
Ejection Doubling (CW 11/7/22)
Skidding Die Errors (CW 8/15/16, 11/27/17)
One-sided double-strikes (ES March/April 2000, Jan/Feb 2002, July/August 2003)
Flat Field Doubling (imperfectly aligned proof strikes) (CW 4/29/13)
Off-center strikes
Chain strikes (CW 4/12/10)
Foreign Object Chain Strike (CW 5/25/15)
Machine Part Impingement (CW 5/25/15)
Saddle (Tandem) Strikes (CW 6/27/11)
Split Plating Doubling
Foldover Strikes (ES July/August 2007; CW 10/10/05, 8/15/11, 1/30/12, 9/15/14)
Edge Strikes (CW 7/18/11, 10/12/15, 3/1/21)
Extrusion strikes (an effect, not an independent error) (ES March/April 2004; CW 10/24/11, 1/15/18)
Multiple strikes (CW 3/30/15)
Indents
Brockages
Counterbrockages
Horizontal lipping (CW 11/30/15)
Die caps (CW 8/6/13, 1/7/20)
Capped die strikes (generic — without identifiable images)
Struck by impaled die cap (CW 6/10/13)
Capped die doubling (doubling associated with capped die strikes) (ES Sept/Oct 2005; CW 6/18/12, 5/16/22)
“Struck-through” errors
Uniface strikes (cross-classified with indents) (CW 7/30/12, 9/16/19)
Sandwich strike (coin struck between two coins or planchets) (CW 5/16/11, 10/31/16, 11/20/17, 5/28/18, 3/22/21)
Nested coins (CW 3/16/20)
Mated pairs (CW 11/9/20)
Bonded coins
Strike clips (ES July/Aug 1999, May/June 2001; CW 6/15/15)
Detached reeding
Coin shrapnel (“breakaway fragments”)
Intra-Strike Damage (damage coincident with strike) (CW 5/30/11, 12/20/21)
Cupping (CW 12/7/09)
Impact-Induced Warping (CW 3/16/15, 1/13/20)
Malrotation Errors (multi-sides coins only) (CW 3/23/15, 11/8/21)
Proof edge lettering errors (generated during strike by segmental collar)