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.
See: http://nicolaa5.tripod.com/articles/Hector/soc/HArms.htm