Note: Do not rely on this information. It is very old.
Broad Arrow
Broad Arrow, a mark which is placed on Government stores, was originally the crest of Henry, Viscount Sydney and Earl of Romney, who was Master-General of the Ordnance from 1693 to 1702. The Broad Arrow is also placed upon buildings, stones, etc., to which special reference is made on the maps of the Ordnance Survey of Great Britain. The height above the sea of these marks is usually given on the maps.