Partial Collar (PAC)
A partial collar error occurs when the collar — the steel ring that surrounds the planchet and forms the coin's edge — fails to rise to its full height before the strike. The planchet is then struck while only part of its edge sits inside the collar. The confined portion receives a normal edge, with reeding if the denomination has it; the portion above the collar is unconfined, so metal spreads outward and leaves a smooth, often beveled band. The result is a coin with two different edges stacked one above the other, separated by a visible step.
Collectors often call this a railroad rim, after the flanged profile of a train wheel; CoinWeek applies the name to level partial collars on reeded edges. Error-Ref, which catalogs this under collar deployment errors, does not use the term, but you will meet it often in listings and forum posts.
CoinWeek calls partial collars relatively common, much more so than broadstrikes and off-center strikes, which makes it a useful first error to learn: it is common enough to handle, dramatic enough to recognise, and close enough to several other errors that telling it apart teaches the distinctions that matter.
How Does It Happen?
The collar normally rises to surround the planchet before the hammer die descends, holds the metal in during the strike, and drops afterwards so the coin can eject. A partial collar is a failure of that rise — the collar gets part of the way up and stops.
Error-Ref describes these causes:
- A tight-fitting or poorly centered planchet pushes the collar partway back down toward the anvil die face, under pressure from the hammer die.
- A poorly centered coin blocks the rise, which can happen on presses with a stationary anvil die and a collar that rises and falls around it.
- Debris becomes trapped between the collar and the neck of the anvil die, so the collar stops partway.
The strike then proceeds normally in every other respect. The dies close with full force, both faces receive a complete design, and the coin's weight is normal — nothing about the dies went wrong. Only the edge records the failure, which is why a partial collar is so often missed by someone examining a coin face-on.
The Named Varieties
| Variety | What distinguishes it |
|---|---|
| Level partial collar | The boundary between the struck edge and the free edge runs parallel to the coin's faces, all the way around |
| Tilted partial collar | The boundary is slanted, so the collar-struck band is tall on one side and shallow on the other. In a severe case one side is fully reeded and the opposite side entirely smooth (Error-Ref shows a 1978 quarter like this) |
| Reverse (reversed) partial collar | Struck in an inverted die setup, with the reverse die as the hammer die, so the collar-marked part of the edge sits next to the obverse rather than the reverse |
| Undulating partial collar | The boundary is wavy rather than straight, which comes from uneven machining of the collar itself |
| Re-entry partial collar | A struck coin that returns to the collar for a further strike has trouble fitting back in and depresses the collar partway |
The tilted variety is the one most collectors meet by name, usually simply as a "tilted collar". Error-Ref treats level and tilted as two forms of the same partial collar error, and the tilted form produces the most visually striking coins in this family.
How to Identify a Partial Collar
- Find the step. Run a fingernail or a loupe down the edge. A partial collar has two distinct zones with an abrupt transition: one with collar contact, one without. That step is the diagnostic, and no amount of circulation wear creates one.
- Look at where the reeding stops. On a reeded denomination the reeding occupies only part of the edge's height and ends at a clear boundary, abrupt or across a beveled band. Reeding that fades, flattens or wanders is wear or damage, not a partial collar.
- Check for the bevel and its machining marks. Where the coin met the collar's beveled entrance, the edge often shows a bevel carrying fine horizontal marks that Error-Ref describes as transferred from the collar's machining. That is a Mint feature; a file or a grinder leaves marks in the wrong direction and the wrong regularity.
- Measure the diameter in both zones. The unconfined part is wider than the confined part. A caliper settles the question when the eye cannot.
- Confirm the faces are fully struck. Both designs should be complete and well struck. If part of the design is missing, the coin is off-center, not partial-collar.
- Weigh it. A partial collar weighs what the denomination should weigh. A light coin points at a planchet error instead.
Partial Collar vs. Similar Errors
| Error Type | Key Difference |
|---|---|
| Broadstrike | The collar never deployed at all, so the whole coin expanded evenly and the edge is uniformly smooth with no step and no reeding anywhere. A partial collar keeps a normal, reeded band. |
| Off-center strike | Part of the design is missing because the planchet sat outside the dies. A partial collar's design is complete. |
| Tilted Collar | The same family: a partial collar whose boundary is slanted rather than level. |
| Collar Break | The collar itself failed — cracked, chipped, or lost a section — so metal pushed into a void at one point on the edge. A partial collar's collar is intact; it simply did not rise. |
| Post-mint damage | A coin ground, filed or squeezed shows tool marks, displaced metal and asymmetry. The partial collar's step is clean, its bevel regular, and its two zones each internally consistent. |
Notable Examples
Partial collars are not a date-and-mintmark error. They occur across virtually every denomination and era of U.S. coinage, and the examples collectors notice are defined by severity rather than by date: a tilted partial collar with one side fully reeded and the other completely smooth is far more dramatic than a slight level collar. Error-Ref's illustrations include a 2000 New Jersey quarter (level, with a machined bevel), a 1978 quarter (severely tilted), a 1996-D dime (reversed) and a 1994-P dime (undulating).
Modern cents, nickels and dimes supply most of the examples in circulation and in dealer stock, simply because production volumes are highest there and modern coins survive in grades where the edge is still readable. The error is found on older material too, but on a circulated 19th-century coin the step is frequently worn to the point where it cannot be separated from damage with confidence.
Collecting Tips
- Describe the severity. A dramatic tilt, a tall free zone, or a boundary that cuts across most of the edge's height are what set one partial collar apart from another. A shallow level collar is easy to overlook.
- Buy the edge, not the photograph. This error lives entirely on the edge, which is the hardest part of a coin to photograph convincingly. Edge-on images, or certification, are worth insisting on.
- Check your change and your rolls. This is one of the error types a patient person can still find unaided, particularly on cents and nickels.
- Record which variety you have. "Partial collar" is accurate; "tilted partial collar, reeding complete at 3:00 and absent at 9:00" is useful to the next person who sees the coin.
- Do not confuse it with a broadstrike. The two are routinely mixed up in listings. If any part of the edge carries normal reeding or normal collar contact, it is a partial collar, not a broadstrike.