Unknown Propellor Slide Rule

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Country of manufacture: ___,            Date of manufacture: ____
Overall length: 25.5 cm,          Width: 5.8 cm,          Weight: 57.2 gms
Materials: simplex design; cardboard
Cursor: no cursor
Scales:
Front:Revolutions per Minute [ Pitch in Inches, Slip % ] Speed in Knots
Slide Back: blank
Back: blank
Gauge Marks: [      ]
Condition: C5 (Normal signs of use)
Came with: Cardboard case; one edge separated

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