This is the small round hole in the corner next to the hardy hole
in English, London Pattern and American style anvils. This is a farrier's (horse shoer) feature for punching and shaping nail holes in horse shoes. In special farrier anvils there is often two pritchel holes. European anvils have a larger round punching hole usually centered at the opposite end from the hardie hole and in recent years three or four graduated holes have been put in anvils.