Unidentified Fascinating Oddity (UFO)

An Unidentified Fascinating Oddity is a die variety that defies classification into established error categories. These are anomalous features on the die surface — raised bumps, unexplained marks, unusual impressions, or atypical design elements — that reproduce consistently on every coin struck from that die, confirming they are genuine die varieties rather than post-strike damage. The term comes from the Wexler Die Variety Files, which use it for varieties that belong in no standard category (a doubled die, a repunched mint mark and so on) yet are unusual enough to list, sometimes where specialists have discussed a feature without agreeing on its cause. Wexler adds that ordinary die chips, cracks and clashes do not belong in it.

How Does It Happen?

Because UFO varieties are by definition unclassified, their origins span a range of potential causes. The common thread is that the feature exists on the die itself (not the individual coin) and was created during some stage of die manufacturing, die maintenance, or die use. Several documented mechanisms produce features that end up classified as UFOs:

Contamination During Hubbing

During the hubbing process, foreign material — a metal fragment, a piece of polishing compound, or other debris — can be trapped between the hub and the die. The hubbing pressure drives this material into the die surface, creating an impression that does not correspond to any design element. The resulting feature appears as a raised anomaly on every coin struck from that die.

Incomplete Die Polishing Artifacts

When the Mint polishes dies to remove clash marks, die cracks, or surface imperfections, the polishing process sometimes creates its own artifacts. Aggressive polishing can gouge the die surface, and partial polishing can leave residual features from previous die events in unusual configurations. These artifacts reproduce on struck coins but do not fit neatly into categories like "die gouge" or "die polish" because their shapes or locations are atypical.

Die Contact Events

Working dies occasionally contact objects other than planchets or opposing dies during their service life. A die that strikes a collar fragment, a broken feed finger, or a piece of machinery sustains an impression that transfers to subsequent coins. If the contact event produces a feature that does not match the profile of a known error type, it receives the UFO designation.

Hubbing Anomalies

Irregularities in the hubbing process can produce features that are not doubled dies, not trail dies, and not any other recognized hubbing variety. These anomalies are legitimate die varieties with consistent reproduction, but their exact mechanism of formation is not determinable from the finished product.

Multi-Cause Features

Some UFO varieties result from a combination of events. A die that was clashed, then polished, then re-hubbed, and finally cracked can exhibit compound features where the individual contributions are impossible to separate. The interaction of multiple die events creates an anomaly that transcends any single classification.

How to Identify a UFO Variety

The identification of a UFO variety involves confirming that the feature is a genuine die variety and then determining that it does not fit any established category:

• Die consistency: The feature appears in the same location, with the same shape and size, on every coin struck from that die. This is the fundamental test that separates a die variety from random post-strike damage. Comparing multiple coins from the same die pair confirms consistency.
• Raised or incuse profile: UFO features can be raised (from an incuse impression on the die) or incuse (from a raised feature on the die). Examine the feature's three-dimensional profile under magnification to understand its relationship to the die surface.
• Location relative to design: UFO features can appear anywhere on the coin — in the fields, on design elements, across lettering, or near the rim. Their position does not follow the patterns typical of known error types.
• Exclusion of known types: Before designating a variety as a UFO, rule out all standard classifications. Is it a die chip? A die gouge? A clash mark? A trail? A doubled element? Wexler's files exclude ordinary die chips, cracks and clashes from the category, so a feature that is simply one of these is not a UFO.
• Die markers: Document the die markers (minor scratches, polish lines, die chips) associated with the UFO die. These markers allow other collectors to confirm they have a coin from the same die and authenticate the variety.

UFO vs. Post-Strike Damage

Notable Examples

Lincoln Cent UFOs

The Wexler Die Variety Files list Lincoln cent UFOs for 1949, 1956-D, 1980, 1990, 2004, 2012 and 2017-P, each naming the person who submitted it.

Presidential Dollar UFOs

Wexler's files also carry a UFO listing for the 2007-P Presidential dollars, the third series in its UFO section.

State Quarter UFOs

Wexler lists Washington quarter UFOs on the 2005-P Minnesota, 2015-P Delaware (park), 2016-P West Virginia (park) and several later quarters. The 2004-D Wisconsin "extra leaf" quarters, with an extra leaf-like shape beside the corn ear, show how long such a feature can stay unexplained: a die gouge is the usual explanation, the Treasury Inspector General's report gave no specific cause, and a deliberate-alteration theory has also been published (search).

Collecting Tips

• Documentation is essential: Because UFO varieties lack a standard classification, thorough photographic documentation is critical. High-resolution images showing the feature under multiple lighting angles, alongside die markers, establish the variety's legitimacy and enable other collectors to identify additional examples.
• Multiple specimens strengthen attribution: A single coin with an unusual feature could be post-strike damage. Two or more coins showing the identical feature in the same location, with the same die markers, confirm a genuine die variety. Seek additional specimens from the same die pair.
• Evolving classifications: Today's UFO designation can become tomorrow's recognized category. As numismatic research advances and more examples surface, some UFOs are reclassified into standard categories. Collecting UFOs is participating in active numismatic research.
• Investigative specialty: The category suits collectors who enjoy analyzing features, debating causes and adding to the published record.
• Online communities: Forums and social media groups dedicated to die varieties are the primary venues for UFO variety discussion and attribution. Sharing images and analysis with experienced collectors produces better identifications than working in isolation.
• Attribution: The Wexler Die Variety Files accept submissions for the UFO category through their coin examination service; good photographs and die comparison images make the case.