I'm not sure if this is what you're asking for but I'm working on an old French bike now which has a Simplex four speed drive. The shifter boss cylindrical portion measures 9.0 mm in diameter and is 5.6 mm tall. There is a square base under this. The screw thread is 5 mm but it appears to more coarse than the normal 5mm fastener. I don't have a metric thread gauge.



This is the shifter.