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Weems and Plath Nautical Slide Rule FNS-3

• Type: Circular
• Size: 8 Inches / 20 cm
• Material: Plastic
• Scales:
  • Front: Speed / Distance / Time
• HvH: 2650

A slide rule to support the Weems System of Navigation. The square base has the distance index arrow and the speed scale. Distance and time are on the lower, larger disk. The upper, smaller disk carries the speed and time indices. With instruction sheet, which I'll let speak for itself. In heavy paper envelope.

This unit is still available from the manufacturer, Weems & Plath of Annapolis, Maryland, as the Nautical Slide Rule 105. You can even download the manual for it as a PDF file. Or read the manual that came with this unit. They say exactly the same thing.