Goodby to the 20th Century.
Space shuttle stamps issued in 1998. (Left): without using an optical decoder. (Right): Hidden texts appear by using an optical decoder.
Pioneers in Communication (my favorite USA stamps issued in 1996).
Dr Sun Yat Sen on a US stamp issued in 1961
Dr Sun Yat Sen stamp on a cover in 1961
A letter from Kaoshiung to USA in 1958.
A diplomatic letter form Egypt to USA in 1956.
