According to Bill Marx, Harpo's top hat is in one of his prop trunks with his other props. In the list of props, there's only one top hat mentioned. Bill said he packed them for Harpo and they're still in the trunks just as they had been when Harpo lived. It was Bill's responsibility as Harpo's prop man. This info came from Bill's book, "Son of Harpo Speaks." I thought you might be interested. It's still fun to imagine having something that belonged to Harpo.