Schön cups the ring in his hand, the other passing back and forth above it as he studies it. "Hm? Indeed. The shell of a creature called an ammonite, ancestor to the chambered nautili of today. Their fossils have a tendency to house fascinating crystals, or to turn in part to opal. The rune on the back is a sign for good health." Does he feel any different, wearing it? Schön is trying to keep an eye on Steve's reaction and condition, even as he negotiates with the ring.
Perfectly reasonable.