Pr are a red gene roo X a red gene hen. The only thing that is certain about the parent of PRs is that both parents were red gene birds. As I stated in my post, most hatchery PRs are the offspring of two PRs.
The original Production Reds were RIR X NHR cross. Most of the ones sold by hatcheries today are simply PR X PR, but no matter which combination of red gene chickens is used for breeding them (RIR, NHR, or PR), all Production Reds are red gene roosters X red gene hens and will produce red gene...