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 sighted side represented looking back into the past, while the forward facing blinded eagle was looking into the future. The blinded side also looks more armoured than the sighted one, representing that, although the future is unforeseen, the blinded side is better prepared learning from the mistakes of the past.[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]