I'll assume you are talking about the Classic & Vintage models from the '60s and '70s. In that case there is not so much a hierarchy as there are simply different models for different purposes. For example the P11 was a tourist model available in '68 and earlier. The P14 was a fixed-gear track model. The P12 (standard 10-speed racer) became the P10 in '69. The P13 was the deluxe 10-speed road racer, and the P15 was the 15-speed "touring" model for '70 and later. If there was any hierarchy between similar models the P13 was the "deluxe" racer with several upgrades as compared to the P12/P10 standard racer. Of course the specific models also differed over the years. More info on model differences here: Schwinn Paramount Model Differences