Well, if you ever wondered about that TCS external loading coil, I found out today when I took that thing apart and that stop pin was  securely attached.  The square drive shaft is held in place by the knob, remove the knob and the shaft comes out the knob end, and a cross pin keeps it from going into the mechanism and contacting the coil wire.  To move that stop, I Dremel tooled the peened part off, and still had to drill into it a bit to get it out.  Moved it over to the spot that aligns with position 6 and soldered it in place.  The coil is  20 turns with a double wrap wire, position 0 is the full coil, dropping 3 turns for each position as you turn to 6, and position 6 leaves 5 turns in line.  Did not have to unsolder anything, just remove screws, but somebody had been in the unit before as it was missing a spacer, plus the coil ends fell apart.  There is an aluminum rod down the middle of the coil form that has glued in place covered ends and the two end screws secure the coil to the frame by that central rod.  When I took the screws out, the end caps and rod fell out where the glue either failed or the other person opened it up.  Probably, on a good unit, if you remove both of the coil mounting screws, the rod would drop into the form, requiring you to open one end to put it in place as you put one screw back in.

The mystery still remains, why the detent was positioned to allow only 3 positions, full coil of 20, 17,14 turns only.

Charlie in NC