It is true that the recommended string tension at the time was in the low 70's, but that was when Prince's customer base was coming from standard-size wood rackets. Prince later changed the recommended tension on their rackets with that head size, and you can safely string them at the tension you would normally use now for an OS. It's nice to know they were engineered to handle the high tensions, though.
If there were such thing as a racket that could instantly improve my on-court results the way the Prince Pro did in 1981, I'd pay a lot of money to get it. (Hmmm... Maybe I should try a Weed.)
I dream of a better world, where chickens can cross roads and not have their motives questioned.