My dad was a USAF fighter pilot; he kept his in-flight circular slide rule around for years. Unfortunately I didn't see it around when clearing out the house ou

My dad was a USAF fighter pilot; he kept his in-flight circular slide rule around for years. Unfortunately I didn't see it around when clearing out the house out after he and my mother died; I know I'd have kept it (because I've still got my yellow Pickett aluminum Model N-500-ES, © 1962).