US naval covers with SA stamps

1968 – Canal Transit Submarine

In 1908, US Congress authorized post offices aboard ships and stations of the U.S. Navy. These post offices offer the same service as do post offices in cities and towns, and have identifiable postmarks. Around 1930, collectors began sending their own covers to U.S. Navy ships to be cancelled and returned. These envelopes or postcards that have been postmarked on and mailed from a navy ship are commonly referred to as naval covers. Also around this time, printed, stamped or hand drawn designs were added to naval covers. These designs, known as

1967 – Tautog Launching

cachets, became popular. The cachet may be specific to a ship, an event, or may be generic in design. Collectors today continue to send covers to ships for servicing. Covers commemorating keel layings, launchings or ship commissionings are popular with collectors. After 1965, some of these covers were issued with the Salvation Army stamp, which must be the ultimate contradiction: The Army without guns commemorated on naval covers. More covers are shown here. Source: About Collecting Naval Covers