He took over in the early 90s. The quality of materials and workmanship was definitely higher back then and many of the designs are considered classics. They also had lower production numbers.
I've owned or played with Schön cues from most eras and do repair work in the Milwaukee area. I prefer the Runde era cues, but they still made a quality product into the early 2000s.
Couple things I would look out for when buying a Schön:
1) Avoid the "acme" joint from the mid 90s. It's a short 5/16-14 pin, stainless joint that is capped at the bottom. I had two, both were butt heavy. They played and hit horrible. I tried multiple Schön shafts on these butts, however even my favorite didn't feel good. The shafts from these cues hit great on other Schön butts.
2) Be extra mindful of dark stained forearms. I've had more than one customer ask if I could fix the "creaking" noise or buzz in their beautiful cue with sentimental value... Check the joint area in forearm for cracks, epoxy fixes, or epoxy filler, that a dark stain can hide.
3) Modern Schön are not the low production, high quality cue of the past. They pump out a shit ton of cues with questionable designs. LTDs don't feel limited, Uniques don't feel unique, and Specials aren't very special.
4) They are pretty expensive for what you get. Even a STL1 is pushing 1k at Seyberts and the more intricate these cues get, the worse they play. For the same money, I'd grab a Jacoby, basic Runde, or Mike Durbin before considering another Schön.
5) If you live in Milwaukee and own a Schön it will happen. "Whoa!? We have the same cue!?!?"
My favorite, "I see your Unique is identical to mine except yours has Cocobolo inlays....mine are Kingwood."
6) See if you can do unchalked test hits on multiple shafts, pick the best one. If no shafts fit the bill, the butt might be deadwood.
Good luck in the search, this has been my experience over the years. Hope you find a nice one.