The Convention of The Baronage of Scotland 
The Crest
Clan chiefs sanction the use of their crest as a crest-badge by their clansmen, in which form it is customarily surrounded by a belt and buckle to distinguish it from the chief’s own crest, which is his personal property.
The image at the right shows a cap badge with the three eagle feathers of a chief with the crest encircled, without the belt and buckle which would be used by one of his followers, and with the coronet of an earl.
Using the crest as a badge is explained in detail on the Lyon Court page here.
