HARTFORD, Conn. (AP) — An exceptionally rare 15th century porcelain bowl made in China that somehow turned up at a Connecticut yard sale and sold for just $35 was auctioned off Wednesday for nearly $722,000.

The small white bowl adorned with cobalt blue paintings of flowers and other designs — one of only seven such bowls known to exist in the world — was among a variety of Chinese works of art sold by Sotheby's as part of its Asia Week events. The names of the seller and buyer were not disclosed.

Sotheby's had estimated the value of the artifact at $300,000 to $500,000. Wednesday's auction in...