If you look up these cards, you'll find them variously dated as 1972, or 1973, or 1974, or 1975. PSA dates this set as 1975. PSA is wrong, off by two years. The problem, I think, is that the Guitar Album compilation produced by Polydor was issued in 1972 and immediately re-issued in subsequent years in different formats. However, the album that corresponded to these cards was issued in 1973, and so were the cards.
PSA is not to be automatically trusted when it comes to information about music cards. Another example is the Dutch Serie P set, which PSA dates as 1973, and that is also wrong, because the set includes Carl Douglas in his Kung Fu Fighting costume, and that song wasn't released until 1974. These dates matter, because a sizable number of music card collectors are extremely interested in musicians' first cards. Whether they ought to be considered "rookie cards" is probably a matter for a future thread, but in the meantime the first card is the equivalent. Look up a famous musical act on eBay + "rookie card" and you'll see what I mean, the quest is already on, and it is spreading.
This little set, for example, features at least 4 first cards -- or as I will personally refer to them, because I personally believe the status is warranted for music cards per guidelines specific to music cards but still similar to sports, at least 4 rookie cards: Duane Allman, B.B. King, Albert King, and Freddie King. I am fairly certain it's also the rookie for Shuggie Otis, and I'm sure a handful of others, too, e.g., I cannot imagine John McLaughlin ever having a card or sticker before this set. 4 Hall of Fame rookies in one potent little set. Plus an early 70s Hendrix card. Plus a Clapton and a Townshend.
If it's incorrectly dated 1975, however, then perhaps another Allman Brothers card from a 1974 could be mistaken as Duane's first card. I don't believe such a 1974 Allman card exists, but it's the principle. PSA is not yet as reliable a source for information about music cards as it is about sports cards. The most accurate source for music card information is David Halpen's website. Halpen is the world's premier music card collector and the world's premier expert on music card information. I've been consulting with him about these sets, in order to make sure that everything here is as accurate and as complete as possible. Soon, TCDB will go from having dreadfully sporadic music pages to being the world's best resource for music card info.