noun Date: 1932 a philatelic cover franked with a newly issued postage stamp and bearing the postmark of the first day of issue and an officially chosen place of issue
FIRST DAY COVER
Meaning of FIRST DAY COVER in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012