Gilson Bearing Averager

Data:

• The device was apparently manufactured for the U.S. Navy.
• It has a mechanical linkage that finds the midway point between two compass bearings. Not a weighted average, just the midpoint.
• Also, the range of allowed inputs is limited.

Questions:

1. What might be the purpose of the device? Its construction seems too complicated to justify the limited calculations of which it is capable. Even if a sailor were not skilled with numbers and could use a device to assist with simple nautical calculations, what would be the purpose of a device that only calculates a simple, unweighted average of two numbers, and only over a limited range?