At Sandan, 3rd Degree black belt, the student, now teacher and with the title of “Sensei” is invited to create their own badge or family crest. They can choose anything and it usually is something very meaningful and not often revealed to the student in detail
Some Family Crest meanings (click link):
Kyoshi John Core’s crest ‘Sei Do Kai”
Renshi Brett Walker’s crest "Ryu no Seishin”