I just recently purchased a 1993 schon, pictured below.
After testing 4 different shafts and 3 different cues, all with 5/16x14 pins, I thought I'd share my test results. I'm sharing this info as I've seen questions on here regarding these pins but there seems to be conflicting information regarding them.
Schon (1993), Adam & Joss
Joss is a 2003 and the Adam was purchased new last year.
Mezz WD700, Predator Pre-Cat, Schon Pre-94 & Schon 1993.
I'm calling the one Schon shaft a Pre-94 as it has the logo on the collar but not sure when it was made.
1993 Schon (Butt)
The Mezz WD700 & Predator Pre-Cat fit on the 1993 Schon. Also, both Schon shafts fit the Schon Butt. I also tried 2 generic 5/16x14 shafts on the 1993 Schon and all worked fine.
Even with the odd pin the 1993 Schon doesn't seem to have problems fitting aftermarket shafts.
1993 Schon (Shaft)
Obviously, the 1993 Schon Shaft fit the 1993 Schon Butt, however, it did NOT fit the Adam or Joss.
I couldn't get the shaft to screw onto the Adam. The shaft screwed onto the Joss but stopped about 1/4 from the end. See pics below.
Also, The Pre-94 Schon shaft fit on the Schon, Adam & Joss
The Schon Pilots
In the last picture is a close-up of the pilot on the two shafts. The left shaft is the 1993 & the Pre-94 is on the right. The Pre-94 is slightly concave and the 1993 is flat.