Alidade, military, wood / brass, made by Aston & Mander Ltd, London, England, 1914
Rule, single-sided, wood to which brass end pieces that lift to 90 and act as sighting elements are bolted by four bolts each. Map reading scales are marked on each bevelled edge of the rule.
For military (gun laying) or survey use.
Used with a plotting table. The rule is laid on the plotting table upon which an ordnance survey map has been placed; a landmark is sighted using the visual cursor provided by the two end pieces so that the bearing of the landmark can then be accurately plotted onto the map.
Aston & Mander Ltd, Makers, London, 1914 No. 1983 - Broadarrow in large "D"