Arms in Scotland is a Monomark, and once achieved in Lyon Court is inherited property. Arms or a crest is not general to a family, although with heraldry you can tell what family line an armiger comes from in about ten seconds. In the old days, the stamped metal copy of the crest of the Clan Chief or Chieftain's (or amigerous Duine-uassail) Arms was usually worn with a strap around the neck of the 'retainers' (a pale, insufficent word for the fiecely loyal ghillies, tacksmen, cousins and kinfolk that were part of the Head of a Derb-fine or Gil-Fine family's tail or household - usually of the same name or related - and if not related, entwined by fealty, services and the land. That is where the Strap and Buckle with the Chief's Crest comes from that we wear in our bonnets today.
I was bribed with dinner and drink to gave a little talk once to a Scottish group on Heraldry once.
http://www.theclanshaw.org/page14.html