ANTIQUES ROADSHOW host Mark Walberg gets a taste of Tucson, Arizona, history from the seat of an antique buggy, part of the impressive stable of horse-drawn conveyances housed at the Tucson Rodeo Parade Museum and proudly mobilized for the annual Tucson Rodeo Parade. At the Tucson Convention Center, it's a pageant of prized possessions, including two Picasso-designed vases bought in France; a court affidavit submitted by Jimmy Carter to the state of Maine on the eve of the 1976 election appealing their decision list him on the ballot as James Earl Carter; and an ornate saddle - purchased for the owner as a child and ridden just once when she competed for the title of Coolidge Cotton Days Rodeo Queen in Coolidge, Arizona - a cinch to bring $6,000 to $8,000.