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上海计算尺厂 1005型飛魚测绘计算尺
Shanghai Slide Rule Factory Flying Fish 1005 Stadia Rule

• Type: Stadia Duplex
• Size: 10 Inches / 25 cm
• Material: Plastic
• Scales:
  • Front: K AI A [ B tgα sinα/tgα sinα C ] D 常数 DI P
  • Back: Ln_-1 Ln₀ Ln₁ A [ B 1-cosα ½sin2α ] D lg 1/60

Stadia rule for surveying.

常数 literally means "common numbers". This scale is a useful set of constants relating to the shape and size of the earth.

With plastic hardcase and manual in Chinese.