Battenberg Course Indicator Mk III, Mounted for Display

Here is an original naval Battenberg Course Indicator Mk III.  The Battenberg course indicator is a mechanical calculating device invented by Prince Louis of Battenberg in 1892 for taking station on other vessels whose range, bearing, course and speed are known. By extension, it has a range of other functions related to relative velocity calculations.

A number of versions of the device were produced and it proved particularly useful for station-keeping, such as ships moving in convoy during World War II.

This example is made of an aluminum alloy, with a clear circular rotating dial and two metal arms, and mounted on a framed wooden base for display.