Declination correction for marching compasses - with graduated disc in base adjusted through aperture in rear plate

摘要

The magnetic compass declination correction device consists of a calibrated disc graduated with east and west declination markings and alignment pointer. The disc has a central hole which engages with a pivot directly below the compass needle bearing point (5). The declination disc has a small hole near the circumference which may be aligned with an aperture (10) in the compass bade plate. Normally, the declination disc is rotated with the manual rotation of the compass rose due to friction contact between the two.