3. Inverted perforations: The only issue on which they are obvious is the 1976 24¢ and 31¢ Bicentennial souvenir sheets. These are $l,000-plus items.
Type 3: The United States 1976 31¢ Bicentennial souvenir sheet (Scott 1689v), along with the 24¢ souvenir sheet of the same issue, is the only issue with obvious inverted perforations.