A medieval artifact bought for $20 at a flea market was initially intended to be used to decorate a garden—but now it fetched thousands of dollars at auction.

The thrifters were left stunned after auctioneers revealed it was a 600-year-old medieval hand cannon dating back to the 1400s.

The bronze gun powder weapon was purchased in Hertfordshire, England to be used as a garden ornament by its owner who had no idea of its true value.

It was sold this week by Hansons Auctioneers for £2,000—more than 200 times its flea market price.

Mystery surrounds how the original seller came to own the cannon but soil residue found inside suggests it would have been dug up at some point.

"It's a rocket of a find," said auctioneer Charles Hanson. "Perhaps it was used by a knight in shining armor. In more than 20 years in the antiques business I have never seen one like it."

"When we came to assess it properly, we were amazed. It's a heavy, triple-ring cast cannon—a type of weapon that was widely used in China beginning in the 13th century, which later made its way onto the battlefields of Europe.

"It was the first true small weapon of its kind, the most mechanically simple form of a metal-barrel firearm.

"Until now, my only knowledge of late medieval hand cannons has come from reading about them in reference books."

The first recorded use of this type of gun powder weapon was around 1330 by two mounted German knights, wrote Hansons Auctioneers. By 1340, weapons like these were widely used in France.

"Originally this cannon would have been mounted on wood with a powder bag and ram rod. It evolved to become a match-lock firearm with trigger.

"It really is a remarkable find," said Charles.

"It's incredible to think this historical treasure ended up in a rock garden."

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