How about this for bargain-hunting? A small bowl bought for $35 in a yard sale in the US turned out to be a rare 15th-century Chinese artifact possibly worth $500,000.

The porcelain bowl – with delicate floral motifs – was acquired by a buyer, whose identity is being kept secret, in the northeastern state of Connecticut.

The buyer had the item appraised by ceramics experts at Sotheby's, first by sending photos, then by taking it into the auction house for a closer look. 

Experts said it was painted for the court of Emperor Yongle, the third emperor of the Ming dynasty who ruled from 1402 to 1424.

"There are only six (other) such bowls known in the world. It is a very exclusive group," Angela McAteer, head of Chinese artworks at Sotheby's in New York, told AFP.

Sotheby's will put the newly discovered seventh bowl up for auction on March 17, when it is expected to sell for between $300,000 and $500,000.

Five of the bowls are in museums: two in Taiwan, two in London and one in Tehran. 

The sixth was last seen on the market in 2007, said McAteer, meaning interest in the auction from private collectors and institutions is likely to be keen.

Many Chinese artworks entered collections in the West in the 19th century before being passed down through generations.

But McAteer says experts are unlikely to ever know exactly how the bowl made its way from China to the junk sale.