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The 11ft 9in (3.58m) seesaw was catalogued as 'rare' but - particularly, as the wood had been replaced - the £600-1000 estimate did not seem unduly conservative.

"I would agree the estimate seemed a bit bullish," said auctioneer Rupert van der Werff, "but this was the first example of its type we had seen so it can be fairly described as rare."

Sealed-bid hopefuls concurred. The seesaw sold at £15,000,

"Compared to many areas of the art world it is still a very small amount of money for a fun, functional, rare and sculptural lot," said Mr van der Werff.

The sale on May 23 offered 530 lots and it followed the auctioneer's 118-lot auction on May 21. With the sealed-bid sale having estimates considerably lower, there was also an early 20th century wooden summerhouse that stood 10ft 1in high, 7ft 5in wide and 6ft 2in deep (3.08 x 2.26 x 1.85m) and tripled predictions, also selling at £15,000.

The buyer's premium was 25/20/12%.