What's the most expensive item ever appraised on the Antiques Roadshow?

"Three items are recognized as the most valuable item featured on the American Antiques Roadshow. A Navajo blanket valued at between $350,000 and $500,000, appeared in Tucson, Arizona in 2002 [1], a painting by 19th-century marine artist James Buttersworth valued at between $250,000 and $500,000 appeared on the 10th season premiere episode, filmed in Tampa, Florida in June 2005, and a mid-16th-century Milanese parade helmet crafted from a single sheet of metal and then highlighted with gold, estimated to be worth at least $250,000. A fourth item, which was appraised at one million dollars was a collection of signatures from every Presidential cabinet member from the Washington administration to Franklin Roosevelt. The owner of the collection declined to appear on the show.  more