ANTIQUES ROADSHOW host Mark L. Walberg and appraiser Colleene Fesko tour the Tucson Museum of Art, rounding up works of art depicting horses. Highlights include: a rare collection of 1956 Olympics memorabilia; World War II American propaganda posters; and a trio of paintings by acclaimed 20th-century French "outsider" artist Gaston Chaissac, given an auction estimate of $50,000-$100,000.