Start with restraint. Do not clean, polish, scrape, bend, squeeze, or chemically treat the coin. Those actions erase evidence and can turn an interesting piece into ordinary damage.
What this classification means
A defective planchet separates before striking, leaving a thin coin with weak or incomplete design. A useful identification does more than name an unusual shape. It explains when in production the feature formed, what physical evidence should remain, and which ordinary forms of damage can imitate it.
Diagnostic evidence to record
Check reduced weight, granular split surface, weakness across the design, and absence of post-mint grinding marks.
- Compare with certified examples and mint-production references, not viral price claims.
Repeatable method: start with Error or damage?, then use the identification workflow and value guide. The page below should add evidence specific to this error class, variety, coin, or damage lookalike.
Common lookalikes and failure points
Acid thinning, lathe work, filed coins, and delamination after circulation can look similar.
A practical examination sequence
- Confirm the host coin. Identify denomination, design subtype, date, mint, composition, and expected weight.
- Describe before naming. Write what the metal actually does without using a marketplace label.
Value factors
Research standard
Use United States Mint production references to understand how blanks, planchets, dies, collars, and presses work. Use major grading-service references to compare diagnostic language. Treat marketplace descriptions as leads to investigate.