Hi Tom,
If you look on the inner ring of the freewheel (where you'd put the removal tool) and see the letter "M" stamped into it, then you have a metric SunTour freewheel. If it's blank, it's English thread. No, the M does not stand for Mario or Masi...
Cheers,
Mark Ritz
Cloudy Arcata, CA
http://www.kinetic-koffee.com