I've never been a big fan of collars, and I didn't feel a need to solidify a relationship by justifying it in that way.

I have changed my mind though, and I do like our own unique version of the collar

We are poly and do have primary relationships as well. So while I am owned I am always secondary in the relationship.
He wanted something to show ownership, and at first wanted a locking collar to which he had the only key to.
That didn't work for me, and we ended up agreeing on a hood peircing and hanging an ownership tag from that.

I'm pretty happy with it as of now, and it does feel pretty special to me.