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A blue diamond ring that child star-turned-diplomat Shirley Temple wore for decades is going up for auction.

Sotheby's says the 9.54 carat ring is among the more than 300 lots in the "Magnificent Jewels" auction scheduled for April 19 in New York. It has a pre-sale estimate of between $25 million and $35 million.

Sotheby's says Temple's father bought the cushion-cut stone for her around her 12th birthday in 1940 for $7,210. She wore it throughout her life, as can be seen in a photograph from The Associated Press from September 1969.

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"This was a treasured piece of jewelry that she wore and enjoyed her entire life," said Frank Everett, sales director for Sotheby's jewelry department in New York.

A model holds a 9.54-carat Fancy Deep Blue diamond ring once owned and worn by American icon Shirley Temple during an auction preview at Sotheby's auction house in New York, New York, USA, on 18 March 2016. Justin Lane / EPA

The actress was the immensely popular star of numerous movies in the 1930s, known for her bouncy curls and outgoing personality. As Shirley Temple Black, she had a long career in public service. She died in February 2014 at the age of 85.

Everett said that the ring had been sold by her estate to a private buyer and that buyer was now putting it up for auction.

The ring is being sold in its original platinum and diamond setting, and a gold setting Temple had made for it will be included as well, Everett said.

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