This is the "Sports Illustrated" preview issue for the 1966 Masters Tournament. Fittingly, the cover subjects are Arnold Palmer and Jack Nicklaus. Nicklaus and Palmer were at the top of their game in 1966. Quite amazingly, the two legendary golfers had alternated winning the prior for Masters Tournaments - Arnold Palmer in 1962, Nicklaus in '63, Palmer in '64, and Nicklaus in '65. And sure enough, Jack Nicklaus would win once again in 1966. 

This full original April 5, 1966 magazine is beautifully autographed by both Jack Nicklaus and Arnold Palmer. 

Full Letter of Authenticity from James Spence Authentication (JSA)