Zeppelins (Zepps) – a nickname for the stamps issued in 1930 for use in conjunction with the flights of the Graf Zeppelin and other rigid airships.
Z Grill – a type of grill used on the 1867 issue that measured about 11 x 14mm in size and with short horizontal ridges. The “Z” grill does not look like a “Z”; legend holds it that William L. Stevenson could not decide which family of grills the stamps belonged to and called it “Z.”
Zion National Park – the National Park honored on the eight cent National Parks issue of 1934, featuring the “Great White Throne”
ZIP Code – (Zone Improvement Plan) First introduced in the late 1960s, this five-digit number facilitates the sorting of mail. The first three digits identify a major city post office, and the fourth and fifth digits identify the delivery area of a post office branch.
Zone – A precursor to the ZIP code, a “Zone” provided a number as part of addresses in many large cities from the 1940s until ZIP Code system was implemented in 1963, and facilitated the sorting and distribution of mail in the same manner as the ZIP.