I was recently gifted some machinist tools and amongst them is a Starrett no. 454 vernier height gauge that had been wrapped in some kind of clear plastic, and perhaps oiled prior to being wrapped, then left in the box for a decade or three. The plastic was brittle and came off without issue, but there remains a residue and the lower arm and marking tool are firmly stuck in place. Thus far I have tried, in order of application: mineral spirits, acetone, ultrasonic cleaner with simple green, WD-40, brake cleaner and penetrating oil...and it cleaned up a little but is still stuck. I am considering evaporust and electrolysis next. What else may help?