英国 - Thomas Mercer 两日制科学测绘航海计时表 - 军事装备 - 1943

出售，这个来自军方的杰出样本
由 Thomas Mercer Ltd.（St Albans）出品的铝质外壳调查用精密计时器，直径4英寸的表盘，是二十世纪中叶极为专门化的精准时钟观测仪器。

. 外壳：
被封装在一个坚固的圆柱形铝制筒状箱(或罐)中，设计用于便携性与野外耐用性。 上盖印有军事标记，如 MoD Broad Arrow。 这就是它的样式。

. 时间等级：
这些仪器通常以恒星时间（以地球自转速度相对于固定星体的速率来调节）来标定，而非太阳时，因而在陆地、海岸线及水文测量工作中具有不可估量的价值。

. 历史背景
Thomas Mercer Ltd. 于1858年在伦敦创立，1874年将主要工作移至 Eywood Road, St Albans。 Mercer 自20世纪20年代起开创了这些电接点改装。结合棱镜星盘，这些铝制外壳的专用单位使测量人员在野外能够以令人难以置信的高精度（最高达1/20秒）确定Exact纬度和经度坐标。
序列号 16847：根据 Mercer 的生产档案，16xxx 系列的序列号出现在二战时期（约 1943-1945），当时 Mercer 向英国武装部队交付了大量精密仪器。
它状况良好，但以此年龄，最好进行清洁/维护保养。

An 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.
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 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.
.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. 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.
. 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.