The Aquila is a two-headed eagle, and represents the entire Imperium of Man. During the times before the Horus Heresy, the two headed eagle was blind-folded on one side, and the other had eyes. The backward facing blinded side represented looking back into the past, while the forward facing sighted eagle was looking into the future.[Needs Citation]
Sign of the Aquila
The sign of the Aquila is a hand gesture to show one's allegiance to the Imperium: the user places his hands flat on his chest with thumbs interlocked.
The Aquila is also displayed on Space Marine power armour, and stamped on weapons produced for the Imperium in its Forge Worlds. Bolters, lasguns, tanks, and every other pieces of military equipment are oftentimes displayed with the Aquila on them. The Aquila is also stamped on signets and rings belonging to those serving the Imperial office, in the military or otherwise.[Needs Citation]