英國 - Thomas Mercer 两日科学勘测航海计时器 - 軍用裝備 - 1943

出售的是一件由美国军方发行的杰出范例\n\n由Thomas Mercer Ltd.（位于圣阿尔班斯）的铝质外壳研究用航海计时器，配有4英寸刻度盘，是20世纪中叶极为专业的精密时间观测仪器。\n\n. 外壳：\n嵌入坚固的圆柱形铝制筒形箱（或罐）中，设计便于携带并适合野外长期使用。带有军事标记的印记，如英国国防部的 Broad Arrow。\n. 时间分级：\n此类仪器常以恒星时（以地球自转速率相对于固定恒星来调节）进行分级，而非以太阳时分级，因此在陆地、海岸线及水文测量工作中极具价值。\n. 历史背景\nThomas Mercer Ltd.于1858年在伦敦创立，1874年将主要生产基地迁至St Albans的Eywood Road。 Mercer在20世纪20年代开始引入这些电接触改良技术。再结合棱柱式星盘，这些铝制外壳的专用单位使测量人员在野外能够以惊人的精度（高达1/20秒）确定确切的纬度和经度坐标。\n. 序列号16847：根据Thomas Mercer的生产档案，16xxx段的序列号出现在二战时期（约1943-1945），当时 Mercer向英国武装部队大量提供精密仪器。\n它状况良好，但以此年龄，若能进行清洁/保养将更佳。\n\nAn aluminium-cased survey chronometer by Thomas Mercer Ltd. of St Albans with a 4-inch dial is a highly specialized, mid-20th-century precision timekeeping instrument.\nThe 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.\n .Time Rating: These were frequently 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. \n.Historical Context\nThomas 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. When combined 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. \n. 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.\nIt is in good condition, but at this age it would be good to have it cleaned / serviced.