 | October 12, 1990 45¢ Multicolored Tropical Coast Scott #C127 |
 | April 27, 1991 50¢ Multicolored Harriet Quimby Scott #C128 |
 | May 17, 1991 40¢ Multicolored William T. Piper Scott #C129 |
 | June 21, 1991 50¢ Multicolored Antarctic Treaty Scott #C130 |
 | October 12, 1991 50¢ Multicolored Bering Land Bridge Scott #C131 |
 | 1993 40¢ Multicolored William T. Piper Scott #C132 |
 | May 12, 1999 48¢ Multicolored Niagara Falls Scott #C133 |
 | July 30, 1999 40¢ Multicolored Rio Grande Scott #C134 |