In the archive there's a thread with answer from Fred where someone asked how they could duplicate the shape shifting magic from Turn Coat. Fred's response was to give the PC the Shape Shifting power, charge him the refresh, and explain it as a series of downtime thaumaturgy rites performed off camera.
Another question about the Gatekeeper's method of opening ways was met with the suggestion of giving Gatekeeper the World Walker power - explaining it as a mastery of that method of magic.
Your suggestion is clearly in keeping with those suggestions. Add in an explanation of how he spent 20 years working on the ring, using rare ingredients in the enchanting, and you've got the perfect answer for when your players ask "How do I make me one of those?".
Richard