I'll pack it up.This is what mine looks like not sure if it make a difference. Your knife edge looks perfect.
Regarding the step vs. straight stem.... I just did some research, and the newer version is the stepped piston shaft (yours), but the consensus on another forum was that it isn't a big deal as long as you maintain your gear. Short version, SP had some instances of the straight stem piston digging into the old style flat HP seat and getting stuck. The step is meant to limit travel, but the newer concave seats obviate the issue... as does periodic (annual-ish) checking of the HP seat.
Respectfully,
James