I have a signet ring which was given to me for my 21st. It's a crest from my mother's side of the family, which supposedly goes back to (wrong side of balnket) Henry VIII - but there's certainly no-one "upper class" in her recent family now.
I wore it on the little finger of my left hand until I got engated and then put it on right hand, as I wanted my engagement ring to have "solo" glory. I've never moved it back after I got married - but my Mum wears hers on her left hand, alongside her wedding ring (and egnagement ring and eternity ring).
I believe because the stag's head is on a tray, and the tray = a crown, that that is part of the "proof" of the royal lineage - but who cares. It looks pretty. It is part of who I am and I am proud of it. I don't fully undertstand its provenance - but that doesn't make it any less special to me.
Interestingly, my brother, who was given on on HIS 21st, doesn't wear it, although he does now wear a wedding ring.
My dad wears a wedding ring, but also has a plain silver signert ring in a modern (Danish) style on his right hand. But that might be a trendy throwback to the 60s!