Striking errors

Indent Errors: How to Identify a Coin Struck With a Planchet on Top

An indent error is a coin with a smooth, curved, design-free depression pressed into it, the shape of another planchet. It happens when two planchets end up in the striking chamber at once and one lies partly on top of the other. The overlap blocks the die, and the upper planchet is driven into the lower one. Indents are satisfying to identify once you know what to look for, and they're easy to confuse with brockages and with post-mint dents.

How indents form

Planchets are fed into the press one at a time, but feeding is not perfect. Occasionally a second planchet sits partly or fully on top of the one in position. When the dies close, the upper planchet sits between one die and the lower planchet. The die cannot reach the part of the lower planchet that is covered, so the upper planchet itself presses into it.

The result on the lower coin is an impression of a plain, round disc. Where the overlap was, there's no design, just a smooth depression bounded by a curved edge. Where there was no overlap, the coin received a normal strike from the die.

The upper planchet usually gets struck too, though only on one side and often distorted, and it can end up as a separate error in its own right. When both pieces stay together, collectors call them a mated pair, and documenting them takes care; see documenting mated error pairs.

Indent vs brockage: the key distinction

The most common identification mistake is mixing up indents and brockages. Both involve something sitting on top of a planchet during a strike. The difference is what that something was.

If you can see any mirror-image letters or devices inside the depression, you are looking at a brockage. Our brockage identification guide covers those in depth.

Reading an indent: what to examine

1. Measure the curve. The arc of the indent should match the radius of a planchet. If the indenting planchet was the same denomination, the arc should match the coin's own diameter. If it doesn't, the indenting planchet may have been a different size, which is a more unusual situation and needs extra care before you claim it.
2. Check the floor of the depression. It should be smooth or show the surface texture of a planchet. Tool marks, scratches running in one direction, or crushed metal point to post-mint work.
3. Look at the boundary. The transition from struck design to indent should be clean. Design elements stop at the boundary; they are not flattened or smeared across it.
4. Turn it over. Behind the indent, the other side commonly looks weak, flat, or slightly expanded, because the lower planchet effectively had double thickness there during the strike. This opposite-side effect is a useful supporting sign.
5. Weigh it. An indented coin should weigh about the same as a normal coin. An indent pushes metal around; it doesn't add or remove it. Use a calibrated scale, as described in calibrate your scale.

Indents vs post-mint dents and damage

Coins get dented, struck with objects, and pressed against other coins all the time after they leave the Mint. Those marks can look superficially like indents. Here is how they usually differ.

For a broader set of tests, see mint error vs post-mint damage. The single most useful question is whether the design in the affected area is missing (it was never struck there) or pushed down (it was struck and then damaged).

Off-metal and different-size indents

Sometimes the indenting planchet is from a different denomination. A smaller planchet can leave a tighter curve inside the larger coin, and the composition of the indenting planchet won't be visible on the coin itself, since only its shape remains. These pieces draw strong interest from error collectors, which means they also draw extra scrutiny.

• Measure the arc carefully. A tighter-than-normal curve suggests a smaller indenting planchet, but irregular post-mint dents can also have tight curves.
• Look for a faint rim outline if the indenting planchet was a Type 2 with a raised rim.
• Do not attribute a specific indenting denomination unless the evidence is clear. "Indented by a smaller planchet" is a safer description than naming the denomination on a guess.
• Get professional attribution before buying or selling a claimed off-metal indent for significant money; our guide to getting an error attributed explains the process.

Photographing and describing an indent

Indents are shallow, smooth depressions, so flat, straight-on lighting can make them nearly invisible in photos. Use a low raking light so the curved boundary throws a slight shadow, and take a second photo with the light from the opposite side. Shoot both faces, since the weak area behind the indent is part of the evidence, and add an edge shot to show the rim is intact.

When you write it up, describe the position of the indent (for example, along the left side of the obverse), its approximate size as a share of the coin's face, whether any rim outline is visible inside it, and how the opposite side looks. Clear, plain descriptions help anyone giving you an opinion, and they make your own records far more useful later.

Researching comparable pieces

We don't quote values for specific errors. To research interest, look at completed sales for the same denomination and similar indent size: sold indent errors on eBay. Indent size and placement matter, and so does whether the coin is certified. Our post on matching the same error severity explains why a small edge indent and a large central indent belong in different comparison groups.

Drivers of interest include the size of the indent, how much design remains, denomination, whether the indenting planchet was a different size, overall condition, eye appeal, and certification.

To train your eye, compare indents side by side with partial brockages and look for the mirror-image design that separates them.

Frequently asked questions

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