Augmentation of Arms
In An Tir, an augmentation of arms is the highest non-armigerous award that is given for service in an official capacity.
In heraldry, an augmentation is a modification or addition to a coat of arms, typically given by a monarch as either a mere mark of favor, or a reward or recognition for some meritorious act. Historically, Augmentations were usually made to denote military or naval victory, and added to the Arms of the person concerned a visible token of gallantry or conquest (i.e. a hand holding the defeated foe's flag).
In the SCA, Augmentations usually reflect long and distinguished service and often take the form of a reserved charge, such as the Middle's dragon. The Crown specifies the nature of the Augmentation, but the recipient, in consultation of the College of Heralds, figures out how the Augmentation will be added to the existing device.
In An Tir, the kingdom ensign (Checky Or and argent, a dexter tierce sable) was designated as a standard augmentation for the populace of An Tir. This is not an individual award, but rather a permission. That is to say, any populace member is allowed to use it, and it is typically used at the hoist on personal banners.
See: http://nicolaa5.tripod.com/articles/Hector/soc/HArms.htm