Giant's Causeway-shaped stones once used to protect US Open golf champion Graeme McDowell's home club from IRA car bombs sold for just under £20,000 at auction.
The collection of seven hexagonal basalt column sections, which were outside the Rathmore clubhouse at Portrush, Co Antrim, at the height of the terrorist campaign, were auctioned in Billingshurst, West Sussex, with a £10,000 asking price, finally fetching £19,112.50.
After significant interest in the auction room and on the phone, they were bought by an overseas phone bidder, said a spokeswoman for Summers Place Auctions.
The stones were bought by the golf club in 1974 and positioned in the car park between the locker rooms and entrance hall to try to prevent an attack after several other clubhouses and sports pavilions across Northern Ireland were damaged in explosions.
James Rylands, director of the auctioneers, said the stones originated from the famous tourist attraction.
Rathmore - where McDowell, 31, learned to play before going on to win this year's US Open at Pebble Beach and then the match that clinched the Ryder Cup for Europe against the United States earlier this month - bought the stones from a quarry company more than 35 years ago.
The club decided they were no longer needed and got rid of them when they were hoisted on to the back of two lorries last year and taken away. They agreed a nominal fee with a man who wanted them as part of plans to landscape his garden. He sold them on to another man who put them up for sale at the auction.
Catalogue details said: "Preliminary research would suggest that stones of this size and magnificence, with each example weighing in the region of two tonnes, are possibly unique outside their original location and as such represents a 'once only' opportunity to acquire such rarities."
Mr Rylands said: "We've never had anything like this before. It's incredibly rare. We have heard that some people may have carried away stones from the Giant's Causeway before, but nothing on this scale.
"There are very few other locations in the UK, or indeed throughout the world, where there are similar geologically configured stones like these. It's a real piece of history."