United Kingdom - Thomas Mercer Two-Day Scientific Survey...

For sale, this excellent example of a military-issued aluminum-cased survey chronometer from Thomas Mercer Ltd. of St Albans with a 4-inch dial is a highly specialized precision timekeeping instrument from the mid-20th century. The Case: Encased in a rugged, cylindrical aluminium drum case (or canister) designed for portability and field durability. stamped with military marks, such as the MoD Broad Arrow. Time Classification: These were often rated to Sidereal Time (regulated to the Earth's rate of rotation relative to fixed stars) rather than Solar Time, making them invaluable for land, coastline, and hydrographic survey work. Historical Context Thomas Mercer Ltd. was founded in London in 1858 before relocating its primary works to Eywood Road, St Albans in 1874. Mercer pioneered these electrical contact adaptations starting in the 1920s. In combination with a prismatic astrolabe, these specialized aluminium-cased units allowed surveyors to determine exact latitude and longitude coordinates in the field with an incredible accuracy of up to 1/20th of a second. Serial number 16847: Based on Thomas Mercer’s production archives, a serial number in the 16xxx series falls during the period of World War II (circa 1943-1945), when Mercer supplied large numbers of precision instruments to the British armed forces. It is in good condition, but at this age it would be good to have it cleaned / serviced.

估價:$561.85

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