There's an interesting history behind the 1976 SSPC cards which I'm not going to go into in detail because there's a pretty good article about them here on baseballcardpedia.com. Although these cards have a copyright date of 1975, they weren't released until sometime in 1976 and are considered a 1976 set.
As I've mentioned here before, I wasn't a big baseball fan as a kid. Sure, I liked baseball, and since I lived in Philadelphia, the Phillies were my favorite team. But it wasn't until I was a young adult, around 1971, that I really became interested in baseball and the 1970's Phillies were my team.
In 1972, the Phillies were pretty sad sack, finishing with a 59-97 record and 6th in the old NL East. But that was their nadir. By 1976, they finished with a 101-61 record. In 1980 they will win the World Series and remain a dominating team for several years after. They did it with a core of players who were with the team through out much of the decade. To me, these guys are the Phillies.