RE: Rust
Aha! While there is no obvious damage to the side of the piston, or to the exhaust ports, there is a slight coppery coloured scratch on the top of the piston. Forensic evidence points to a wrench accident.
Speaking of geniuses, when I was 14 I wrecked a Babe Bee .049 with the Cox wrench. The replacement piston & cylinder I bought at the local hobby store was of the slitted exhaust type - no way to stuff that up.
I don't even have a Cox wrench suitable for a reed valve .049. I do have a TD one in my TD .049 box, which I only ever intend to use for taking glow heads off.