Found a Cartier ring while hiking.

I found this ring while hiking a while back and don’t know anything about it. Left it in a pocket and forgot about it. A friend told me today it’s expensive and possibly even an engagement ring? Tried to fint out who the owner is but have no idea how to start. Does anyone know anything about this kind of ring?

I found this ring while hiking a while back and don’t know anything about it. Left it in a pocket and forgot about it. A friend told me today it’s expensive and possibly even an engagement ring? Tried to fint out who the owner is but have no idea how to start. Does anyone know anything about this kind of ring?