A UK coin that looks different may be affected by lighting, wear, cleaning, corrosion, damage or normal production variation. Colour, shape or weight alone cannot prove that a coin is rare, valuable or counterfeit.
Check the correct specification
First identify the denomination, date and design. Compare diameter, weight, thickness and composition with a reliable official reference such as Royal Mint information. Use accurate scales and measurements, but treat them as clues rather than a final answer.
Possible explanations
- Normal wear and surface change
- Cleaning, polishing or chemical exposure
- Damage after the coin entered circulation
- Different metal, finish or production specification
- A possible minting or planchet issue
Leave the coin unchanged
Avoid polishing, scraping or chemical tests. Photograph it as found and record its details. If it remains unusual after comparison, seek an independent specialist opinion. Use the errors versus damage guide and the coin research method as next steps.