I'd make it out to be a PR10 also. The 73 catalog
shows that they're practically identical except the painted DO's and 3 tube vs full Reynolds.
Either way I'm sure it is a fine riding bike.
This one seems to include the tubulars as well as a set of nice clincher wheels - of the Helicomatic persuasion I might add. Some people dislike them due to wear concerns but they have their fans, including yours truly. The cranks is a plus too, for some people.
I'd say $400 would be reasonable - though the seller could have at least installed new bar tape for the photo.