Collar Break (CBK)
A collar break error occurs when the collar die — the steel ring that surrounds the planchet during striking and forms the coin's edge — cracks, chips, or loses a section of its working face. During the strike, metal from the planchet flows outward under tremendous pressure and into whatever void the damage has left. The result is a localized deformity on the coin's edge: a raised fin, a nib, a stepped arc, or a missing stretch of normal edge, depending on how the collar failed. The rest of the edge remains normal, displaying proper reeding (on reeded-edge coins) or a smooth profile (on plain-edge coins).
"Collar break" is a family, not a single appearance. Error-Ref catalogs this group as collar cuds, under die errors, and names eight distinct failures within it. They share a cause — the collar gave way — and differ in how much of it gave way, whether the broken piece left or stayed, and whether it then moved. Knowing which one is in front of you is most of the attribution, because several of them can be mistaken for each other or for post-mint damage.
How Does It Happen?
The collar die is one of three dies involved in striking a coin. While the obverse and reverse dies impress the coin's faces, the collar die constrains the planchet's outer edge, giving the coin its precise diameter and edge treatment. On reeded-edge denominations like dimes, quarters, and half dollars, the interior surface of the collar carries vertical grooves that impress the reeding into the coin's edge. On plain-edge denominations like cents and nickels, the collar is smooth inside.
Collar dies endure substantial mechanical stress. Every strike cycle drives the planchet's expanding metal outward against the collar wall; the U.S. Mint gives 35 to 100 metric tons of press force for circulating coins, depending on the denomination. Over time, this repeated pressure causes metal fatigue. A second mechanism is mechanical rather than cumulative: when a hammer die is temporarily misaligned, it strikes the beveled entrance of the collar instead of passing cleanly into it, and those repeated off-axis impacts crack the collar where the stress concentrates.
A collar can outlast the dies it works with. In the 2002-P Kennedy half dollar study described below, the same collar served three die pairings, so a collar flaw can appear on coins from several different die pairs and change across them.
The Named Failures
Error-Ref's collar cud group, from the mildest to the most complete:
| Failure | What happens to the collar | What the coin shows |
|---|---|---|
| Chipped collar | Small pieces break away from the working face | Small raised defects on the edge. On reeded coins these run vertically and often reach from one rim to the other; on plain-edge coins they usually descend from the hammer-die rim and stop short of the other |
| Vertical collar crack | The collar cracks lengthwise, often at two opposite points | Easiest to see on plain-edge coins. Can be the first stage of a bilateral split collar, so it is worth recognising early |
| Bilateral split collar | Cracks at two opposing points spread apart | Two raised nibs at opposite poles, with the diameter enlarged across the perpendicular axis — a round coin turned slightly oval. Collar contact marks survive on both sides of each nib |
| Irregular collar break | A chunk breaks from the upper edge of the working face | An irregular bite of missing metal along the rim, spanning an arc of the coin |
| Complete collar break | An entire section of the working face breaks away | A missing arc of normal edge, beginning and ending abruptly, with a step-up at each endpoint where supported edge meets unsupported |
| Retained collar cud | A section breaks free but stays in place, held by its own seating or by the collar's clamps | The break shows evidence of movement: one endpoint stepping up and the other stepping down, partial-collar steps at differing heights, or a partial collar sloping at different angles on each side |
| Rotating collar cud | A damaged collar turns gradually as it strikes | A collar chip whose position migrates around the edge across coins from the same die pair — the rotation is invisible until a flaw gives it something to mark |
| Catastrophic collar failure | The collar breaks brittly during a strike | Almost never documented. The coin that was in the chamber records the moment the collar came apart |
The retained collar cud is the one most often misidentified, usually as a bilateral split collar. The separation is movement: a bilateral split spreads horizontally and keeps a roughly round outline with nibs at both poles, while a retained cud shows vertical displacement, horizontal offset, or pivoting at the break.
How to Identify a Collar Break
- Localized edge deformity: The defect appears at one point or two on the coin's edge, not around the entire circumference. The affected section is the one that contacted the damaged part of the collar.
- Normal edge elsewhere: Portions of the edge that struck against intact collar look completely normal. Reeded coins show clean, uniform reeding on all unaffected sections.
- Look for the step: On a complete break, each end of the missing arc carries a step-up where the edge passes from collar-supported to unsupported. On a retained cud, one end steps up and the other steps down. Error-Ref calls the step-up a key diagnostic for a complete break.
- Raised metal that flowed: Where the coin pushed into a void, the metal expanded smoothly into the gap, rather than showing the cuts and scrapes of metal moved by a tool.
- Know which rim it starts from: Many collar failures do not run the full thickness of the edge. On plain-edge coins, collar chips usually descend from the hammer-die rim and seldom reach the other rim, and an irregular break bites in from the collar's top edge. On reeded coins, chips run vertically and often reach from rim to rim.
- Measure across the coin: A bilateral split collar leaves the coin measurably wider on one axis than the other. A caliper settles it where the eye will not.
- Compare coins from the same die pair: Progression is the signature of a die error. Later strikes can show a larger defect; on a rotating collar, the same chip appears at a different clock position each time.
Collar Break vs. Similar Errors
| Error Type | Key Difference |
|---|---|
| Broadstrike | No collar confined the planchet at all — the whole coin is wider than normal and carries no reeding. A collar break affects only a section of edge. |
| Partial collar | The planchet sat partially above the collar, so part of the edge is unstruck and smooth while the collar itself is intact. The coin's outline stays circular. |
| Tilted Collar | The collar is tilted rather than broken, producing a beveled edge — thicker on one side of the coin and thinner on the other, all the way around. |
| Collar Clash | The collar and a die struck each other, marking the die face rather than opening a void at the edge. |
| Die crack at the rim | A crack in the obverse or reverse die produces a raised line on the coin's face. A collar failure shows on the coin's edge. |
Notable Examples
The documented examples below come from Error-Ref's collar cud pages.
2000-D Jefferson Nickel — Complete Collar Break
Roughly 100 arc degrees of edge missing its collar support, with the break beginning and ending abruptly and a step-up at each endpoint. Both die faces on this example show heavy damage as well, consistent with collar fragments or foreign matter loose in the striking chamber.
1989-P Jefferson Nickel — Irregular Collar Break
A large break running from about 10:00 to 1:00 on the obverse, where a chunk gone from the upper edge of the collar's working face transferred as an irregular bite of missing metal along the rim.
1960-D Small Date Lincoln Cents — Chipped Collar
Edge chipping on a plain-edge coin, the mildest end of this family. Error-Ref's images of these are captioned as collar breaks, which is a fair illustration of how interchangeably the terms are used in practice.
1981-P Jefferson Nickel — Vertical Collar Cracks
Cracks at roughly 5:00 and 11:00, with peripheral die damage around the date on the same coin — the combination that supports the misaligned-hammer-die explanation rather than simple fatigue.
1964-D Jefferson Nickel — Bilateral Split Collar
The collar split at two opposing points and spread, striking the coin with a raised nib at each pole. On this example the planchet came to rest midway between the spread sections.
2002-P Kennedy Half Dollars — Rotating Collar Cud
Error-Ref calls this the definitive study of a rotating collar. William "Ed" Eubanks examined 261 examples carrying a collar chip and published the results in Errorscope in 2003: the chip's position advanced steadily clockwise through a full 360 degrees, tracked across nine die stages and three die pairings. Why collars rotate is still not well understood.
1964 Proof Jefferson Nickel Mated Pair — Catastrophic Collar Failure
A struck coin stuck to the hammer die, a second planchet fed in beneath it, and both struck together inside the collar. The combined thickness exceeded what the collar could take and it split at five points. Collars fail far less often than dies, so coins that record the failure itself are rarely documented.
Collecting Tips
- Inspect edges deliberately: Collar failures are easy to miss if you only examine the obverse and reverse. Rotate the coin and look at the edge profile, particularly when searching rolls.
- Reeded versus plain edge: On reeded coins, disrupted reeding creates an obvious visual discontinuity. On plain-edge coins, a small fin or chip can be mistaken for a rim irregularity, so these need magnification rather than a glance.
- Confirm with magnification: At 5x to 10x, metal pushed into a collar void shows pressure flow lines. Filing, gouging and other post-mint damage leave scratches, tool marks, or irregular tearing instead.
- Check where the defect starts: A genuine collar chip or irregular break usually extends down from the hammer-die rim, and a complete break shows the step-up at each end. Damage that cuts in at random heights with tool marks is post-mint.
- Name the failure, not just the family: "Collar break" is accurate but unspecific. Recording which of the eight it is — and the evidence for it, such as a step-up or a measured oval — is what makes an example useful to somebody else later.
- A second coin from the same collar proves it: Because the collar is tooling rather than the coin, the defect repeats. Two coins with the same defect at the same place settle any question of damage.