*USA, 1935–1939, Pearl Harbor Navy Yard Brass Pressure Test Plate, Territory of Hawaii*
A rare and evocative pre-war U.S. Navy Yard identification plate from Pearl Harbor, Territory of Hawaii, engraved: “TANK TESTED TO 300 LBS INTERNAL WATER PRESSURE / DATE ___ / NAVY YARD / PEARL HARBOR T.H.” Stamped twice with testing dates 11-20-35 and 1-4-39 (U.S. date format Month/Day/Year), confirming the tank or pressure vessel was hydrostatically tested at the yard on both occasions. Constructed in solid brass with four corner mounting holes, the plate measures 16.5 cm x 8.4 cm. An authentic relic from the Pearl Harbor naval establishment in the years immediately preceding the United States’ entry into the Second World War.
Historical Note: The Pearl Harbor Navy Yard, established in 1908 on the island of Oahu, became the cornerstone of American naval power in the Pacific. By the mid-1930s, in response to Japan’s growing expansion across East Asia, the U.S. Navy embarked on a major modernisation programme at the yard. Between 1933 and 1940, facilities were significantly enlarged: Dry Dock No. 1 was expanded, Dry Dock No. 2 constructed, and new machine shops, foundries, and oil storage tanks were established to support an enlarged Pacific Fleet.
This brass test plate, dated November 20 1935 and January 4 1939, was issued during that crucial phase of naval rearmament triggered by the Vinson–Trammell (1934) and Naval Expansion (1938) Acts. These measures authorised sweeping increases in shipbuilding and infrastructure to prepare for potential conflict, marking the first major U.S. naval build-up since World War I. As a result, Pearl Harbor’s facilities were extensively refitted and its tank systems—such as those certified by this very plate—were tested to new operational pressures as part of the Pacific Fleet’s strategic expansion.
The engraved suffix “T.H.” denotes Territory of Hawaii, a designation in use from 1900 until Hawaii achieved U.S. statehood in 1959. Within just two years of the final test date on this plate, Pearl Harbor would become world-famous following the Japanese attack of December 7 1941, which brought the United States into the Second World War. Artefacts bearing pre-attack yard markings are scarce survivors from this formative era in American naval history.
*Condition* A genuine and unrestored brass plate displaying age-consistent patination and surface wear, with legible punched and engraved text. The reverse shows heavy oxidation and areas of verdigris from long exposure, likely consistent with shipboard or yard use. Original test dates remain sharply defined with remnants of white marking compound in the numerals. Please see photographs as part of the condition report.
