Wanda Thompson examines a special Pony Express stamp issued July 19, 1960, during a class on philately — the collection of stamps — at the National Postal Museum last week. About 120 million such stamps, with a face value of 4 cents, were printed to commemorate the delivery of mail by carriers riding ponies. The current value of the stamp is about 15 cents. The museum, next to Union Station, holds its “Philately in Action” class every several months. Last week’s class was one of two in October, National Stamp Collecting Month.