Battenberg Course Indicator Mk 5 in Wood Case Wellington The amber lens is removable

The amber lens is removable

and P-38 Lightning

vs wings and tailwheel) aircraft

but it could be cemented in place

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

Battenberg Course Indicator Mk 5 in Wood Case Wellington The amber lens is removableHere 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,