I took Joe Johnston's suggestion and looked it up in the Ford books.
The only caps that were NON-vented were 1953-'59 Full Size Ford cars, except Sedan Delivery, Station Wagon, Retractables, and Rancheros. This catalog only goes to 1959 so the '60 Squarebird will comply with the '59.
Remember, the "S" designation represents Thunderbird models.
The second and last two entries, cover 'LOCKING' gas caps.