Description
For sale is a Vintage Otis King’s Patent Pocket Calculator, Model K, complete with its original box and instruction leaflet. Made in England by Carbic Limited, this is a classic cylindrical slide rule, widely used from the 1920s–1960s by engineers, navigators, surveyors, and scientists for performing rapid mathematical calculations long before electronic calculators existed.
Item Features:
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Model: Otis King’s Patent Calculator Model K
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Type: Cylindrical logarithmic slide rule
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Material: Chrome-plated metal with printed logarithmic scales
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Functions: Multiplication, division, proportion, roots and powers, and general mathematical calculations
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Origin: British Made Throughout
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Included:
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Original black presentation box
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Full instruction leaflet (General Description, Scales, Method of Operation, Examples etc. 8 pages in total)
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Serial number: X5108 (on end cap)
What It Is Used For:
The Otis King’s Pocket Calculator operates as a cylindrical slide rule, offering greater accuracy than standard flat slide rules. It was historically used by Engineers, Surveyors, Mathematicians, Ship navigators, Scientists, Students and technical professionals.
It allowed quick calculation of multiplication, division, square roots, cube roots, ratios, and other operations without needing written computation.
How to Use It (Simplified Overview):
The calculator consists of:
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Outer sleeve (Holder)
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Inner cylindrical scale
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Rotating chrome Cursor with arrows for alignment
Basic Operation
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Set the multiplicand on the Cylinder opposite the Unity marking on the Cursor.
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Rotate the Cursor or Cylinder until the desired multiplier aligns with the pointer.
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Read the answer at the bottom arrow.
The included original instruction leaflet provides full step-by-step examples.
Condition:
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The calculator is in excellent vintage condition, with bright chrome and clearly readable scales.
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The original box shows age-related wear, consistent with storage.
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Instruction leaflet is intact and readable, lightly aged.
Overall, a beautifully preserved collector’s item.
Ideal For
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Vintage scientific instrument collectors
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Slide rule enthusiasts
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Mathematicians and engineers
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Museum displays
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Unique gift for STEM professionals
