Battenberg Course Indicator Mk 5 in Wood Case Wellington The compass was illuminated electrically

The compass was illuminated electrically via bulb mounted in a small compartment over the compass itself

Here is an electric (4V

569432" and  "General Electric Canada"

and presents it to the pilot visually on the Zero Reader Indicator

and P-38 Lightning

Battenberg Course Indicator Mk 5 in Wood Case Wellington The compass was illuminated electricallyHere is an original naval Battenberg Course Indicator Mk 5. 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,