Z

Z GRILL: Two copies exist of the US 1867 1-cent blue Z grill.
ZEMSTVOS: Term used for stamps issued by Rural Districts (Zemstvos) in Russia. Similar to U.S. Locals.
ZEPPELIN STAMPS (ZEPS): Stamps issued for use in conjunction with the flights of the Graf Zeppelin and other rigid airships. Covers carried on these ships are called "Zeppelin Covers."
ZIP: A cartoon character looking like a postman printed on the margins of U.S. stamps and bopklet panes since 1963. The man is referred to as Mr. Zip and is used to encourage people to use the Zone Improvement Plan code. It is always collected attached to the postage stamp.
ZIP+4: Addition of four digits to the basic Zip Code for sorting by carrier route and specific addresses.
ZIP+4 PRESORT: Bulk mail presorted to the nine-digit Zip Code and bundled.
ZIP BLOCK: A margin block of U.S. stamps bearing the inscription "Use Correct Zip Code" in the salvage.
ZUM,ZM: Zumstein Specialized Switzerland and Liechtenstein Postage Stamp Catalog
ZUSÄTZLICH: (Ger.) Increased in any manner. ADDITIONAL (Eng.)