Error coins are coins that have been miss-produced at the mint.
Most should have been spotted at the mint before being released into circulation,
therefore, all tend to be relatively rare.
Some error coins depending on the type of error are extremely rare. Gold ones
tend to be amongst the rarest because they are the coins that are more closely
inspected by the mints.
Error coin collecting is a more specialised coin collecting subject and although
initially error coins were scorned at by collectors, the popularity for collecting them
has increased over the recent years.
Below are several different types of major error coins.