NEW YORK (AP) -- A miniature portrait of Czar Peter the Great in a diamond-encrusted frame -- owned for decades by an Arizona family that didn't realize its historic significance -- has been auctioned for $1.3 million.

Sotheby's auction house says the 18th-century Russian treasure was purchased Monday by an anonymous telephone bidder for 10 times its pre-sale estimate of $120,000. The estate of the original owner, George Roberts, learned of its importance during an appraisal over the summer. Roberts purchased it in 1951 from a London dealer.

Experts believe that as few as 10 of the bejeweled miniatures were bestowed by Peter the Great on his subjects. The 3 1/2-inch-high oval portrait sold Monday depicts the czar in a blue cape and a sash. The frame hangs from an imperial crown.