UFOs: Coin Mysteries Waiting to Be Solved
The Error Types That Defy Classification
An Unidentified Fascinating Oddity (UFO) is a die variety that doesn't fit into any established error category. Raised bumps, unexplained marks, unusual impressions — features that reproduce consistently on every coin from that die, confirming they're genuine die varieties, but whose origin is unknown or debated.
The UFO designation is an honest acknowledgment: "We know this is real, but we don't know exactly how it happened."
How UFOs Form (Maybe)
Because they're by definition unclassified, potential causes span a wide range:
- Contamination during hubbing — Foreign material trapped between hub and die gets pressed in under hundreds of tons of pressure
- Incomplete die polishing — Aggressive polishing creates artifacts that don't fit neat categories
- Die contact events — A die strikes a collar fragment, broken feed finger, or machinery part
- Multi-cause features — A die that was clashed, polished, re-hubbed, and cracked produces compound anomalies
The Wisconsin Quarter "Extra Leaf"
The 2004-D Wisconsin quarter "extra leaf" varieties — showing additional leaf-like features on the reverse corn ear — were initially classified as UFOs before analysis determined they resulted from die gouges. This is the UFO lifecycle: a mystery is cataloged, studied, and eventually reclassified once the mechanism is understood. Today's UFO can become tomorrow's recognized category.
Discussion
- Have you ever found a coin with a feature you couldn't classify?
- What's the most puzzling die variety you've encountered?
- Do you think most UFOs will eventually be explained, or are some truly mysterious?
- Post your unidentified finds here — let's investigate together!