Piper Chuck told you right. There are also a few ringed engines with chrome cylinders out there. There is also a iron cylinder with a ring (not seen much any more), and a lapped cylnider/piston where the liner is iron and the piston is iron or aluminum and there's no ring. This isn't seen much amy more, either.

For all practical purposes, any engine made recently that does not have a ring is a ABC/N. Your OS FX is that type of engine.

Not right, Bruce. It's an Aluminum piston with a Brass cylinder plated with Chrome or Nickle.

Dr.1