Looks like a dot, aka Die Chip I want to share this webpage with you - http://www.coinsandcanada.com/coins-errors-varieties.php?error=dots&id=6
I think its this one, which is also with the die chip: Occasionally, dots can come from gas bubbles (air or other) smaller or larger (pictures below), trapped in the metal. Compressed gases rise in temperature dramatically when striking and they expendent. I don't agreed with the die chip, there nothing there to make a chip, its open field ...