The white porcelain bowl was spotted by an unidentified antiques enthusiast near New Haven last year, and they quickly sought an expert evaluation. The experts came back with good news, revealing that the bowl is thought to be worth between $300,000 and $500,000.
In fact, it is believed to be one of only seven such bowls in existence and most of the others are in museums."
Addendum: Here is the Sotheby's listing (with a detailed description and additional photos). The bowl realized $721,800 USD.