1971 2 Pence Coin Possible Error

The first test to do is to weigh it. An actual mint error would almost certainly weigh differently than a regular 2 pence piece of the same age.

I should perhaps point out that it is unlikely to be a mint error. The coin is quite well-worn; if it were a true mint error struck on a brass planchet, someone surely would have noticed how different it was back when it was shiny and new.

It has most likely been plated with something, or perhaps been in an unusual environment that made it change colour.