When you find a coin that looks like it could be an error, the first question you must ask is whether the error occurred at the mint, or after the coin left the mint. Coins with errors at the mint are valuable. Coins with errors after the mint are damaged and worth zero.
Linda sent us this image of her cool brockage error coin from the Bank of Upper Canada. You can see an error-free example at this CoinQuest link. The intriguing thing about brockage errors is that one of the patterns is reversed, i.e., it is a mirror image of a normal pattern. Obviously, this error occurred at the mint, so Linda's coin is valuable.
Brockage errors always involve two coins that have gotten tangled up in the minting machine. One coin is normal but it has gotten stuck somehow in the machine and is subsequently used to produce more coins. Because it is a normal coin used to strike more coins, the pattern comes out exactly opposite of a normal coin. The coin with the reverse pattern is called a brockage.
Minting error expert Mike Byers looked at Linda's coin and supplied this evaluation:
'Hi Paul and Linda. It looks like an 1850 Canadian half penny token or penny token (can't tell) since its an incuse brockage. The brockage could be a first strike, or a second with a slight obliteration. The value I'm guessing is in the range of US $100, since the condition isn't great. -- Mike Byers'