A stain from a dissimilar material, possibly acidic, that was in direct contact and stained the coin.
An! Thanks for answering! I was convinced I found something unique. Maybe next time. Sent from my iPhone using Tapatalk
This one doesn't appear to be so, but there are nickels with incomplete mixing of the alloys that gives a nickel "stripes". This is especially prevelant on war nickels, but some years are known for having poorly mixed alloys.
The back of the coin appears to have the same discoloration and it is a 2000-D nickel. Quality control of the alloy mixes are much better now then they were back in the 1940's, 50's and 60's.
