My friend is from there and says "I have never encountered one that had an IS, but I have brought my own to a few. I use Therese Kienstra for my appraisals (she is in Clayton, on Brentwood just south of "downtown Clayton proper" 314-862-5054) and she was very intrigued by it when I brought it in.
As for local jewelers, I have never been stared down because of it. My friend''s family owns Saettle''s and my friend herself had never heard of them til I brought mine in. I have also brought it to Mavrik, Genovese, Simons, Lordos, Ellard Heffern, David Kodner, Curt Parker and Hamilton. All were intrigued by it, and a couple of folks had heard about both the IS and PS.
Only one jeweler I know of was pissy about it and that was Vincent''s on Olive...there were a lot of problems with the whole experience with them, and that should have been my first red flag. Very shady."
Hope that helps!