While walking his dog on a river-side path in Bedfordshire, England, a man found an ancient gold penny. After examining it, coin expert Richard Bishop said, "It is quite simply the most important single coin find for a century. We fell off our chairs when we realized what it was."

The 1,200-year-old penny bears the image of Coenwulf, an Anglo-Saxon king who ruled Mercia between 796 and 821AD. There are seven other similar coins in existence, but this is the only one ever found from this time period.

The coin was actually discovered back in 2001, and the exact location is still undisclosed. Why the secrecy? Officials fear the knowledge would trigger a gold rush, starting a stampede of amateur treasure hunters.

Prior to auction, the coin was expected to sell for approximately a quarter of a million dollars. "There is no way of putting a price on it because one hasn't ever been found before. It is unique," Bishop said.

That uniqueness paid off. On October 6, 2004, the coin brought $409,000 at auction. The price made it the most expensive British coin in history. The proceeds will be divided between landowner Fen Reavers and the metal-detector-wielding dog walker who found it.

It really wasn't an accident that this man found the coin. He is an amateur metal detector enthusiast. He has an eye for metal and coins on the ground. He is always looking even while walking his dog.