A friend of mine has recently been collared. She was not collared by a lover or a Dom. She has become the student to a Domme-friend at an organization. She will be in service to the organization and to people who attend there. She will also be under the personal mentoring of this Domme, who will train her in the finer points of being a respectful and classy submissive.... "a more demure slut," as she put it. LOL
As I thought about it, under the right circumstances for the specific student, this is a great way of being collared.