Now showing: United States - Official Penalty Mail (1990 - 1999) - 13 stamps.
22. February WM: None Perforation: 10 vertical
6. April WM: None Perforation: 11
24. May WM: None Perforation: 11
24. May WM: None Perforation: 10 vertical
14. September WM: None Perforation: 11
19. October WM: None Perforation: 11
13. December WM: None Perforation: 10 vertical
9. May WM: None Perforation: 11¼
9. May WM: None Perforation: 9¾
8. October WM: None Perforation: 9¾ vertical