Renovating an old home will always produce surprises-but sometimes the discovery is a treasure that could fund the entire project.

Three stonemasons working on a centuries-old estate purchased by a couple in 2012 in Plozevet, Brittany, found a hidden metal box embedded in a wall.

They were shocked to find it stuffed with rare gold coins, minted during the reigns of French Kings Louis XIII and Louis XIV.

63-year-old Franí§ois Mion, who owns the 13th century mansion with his wife, decided to turn the barn into a living space. When he got the call from his foreman, he "thought it was a joke."

Then, a few days later, above a beam, they discovered a bag containing another stash-which added to the grand total of 239 gold coins.

The cache is being put up for auction on September 29, says Ivoire Auction House, which estimates them to be worth well over a quarter million euros, or $300,000.

The couple submitted the trove to the Regional Preventive Archeology Service for authenticating and analyzing. They determined that the last known inhabitants of the mansion dates back to the mid-18th century, owned probably by wealthy land owners, possibly traders involved in the transport of Bordeaux wines to England.

French law states that the haul will be shared 50-50 between the owners of the property and those who discovered the coins-so the trio of stonemasons are likely lifting a glass to toast their luck.

WATCH a French television report below…

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