Air Ministry Laboratories Position Line Slide Rule Mk. IIa (Bygrave)

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Country of manufacture: England,            Date of manufacture: ____,      Serial No.: 472
Overall length (closed): 23.0 cm,          Diameter (outer cyl): 6.4 cm., (inner cyl.) 5.4 cm.
Materials: Plastic, aluminum, paper. felt
Outer Cylinder: Paper covered aluminum, 6.4 cm in diameter and 18.5 cm long contains instructions for use, correction factors for bubble sextant readings, and two cursor pointers for use on the intermediate and inner cylinders.
Intermediate Cylinder: Paper covered aluminum, 5.9 cm in diameter and 18.2 cm long contains further instructions and a spiral log cosine scale with a total length of 414.3 cm
Inner Cylinder: Paper covered aluminum, 5.4 cm in diameter and more than 22.2 cm long contains a spiral log cotangent scale with a total length of 758.4 cm.
Condition: C5 (Signs of Normal Use)
Came with: Original black metal cannister
Notes: Designed to solve problems in spherical trigonometry, as used in celestial navigation. Further discussion and instructions for use may be found here.

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