Yes, Peter Post was a fine track racer, especially in the six-day races, where he did incredibly well - if memory serves, he is the winningest six-day guy of all time. But don't overlook his roadman prowess. He still holds the record for the fastest Paris-Roubaix winning speed from 1965, give or take (a record that may never be broken, as they changed the course the year after his victory to one that caused average speeds to drop). He also ran the famous TI-Raleigh team of the late 70s and early 80s, a team that included Jan Raas (serious classics palmares), Gerrie Knetemann (a World Championship and a highly respected captain-on-the-road), Joop Zoetemelk when he finally (and deservedly) won the Tour de France, and several others who I am forgetting at the moment.

"Taper gauge" was used for stays and fork blades, not the main triangle (butted at one end, not both). That sticker being oin the seat tube is almost certainly a mistake. Kinda makes it more fun, though.