This is the third Anniversary set BBM has done for the Hawks - they did a 70th Anniversary set in 2008 and a 75th Anniversary set in 2013 (they also did a set in 2015 celebrating the 10th Anniversary of Softbank buying the team but that only covered the years since 2005 obviously). Those sets had 99 cards each in their base sets but the base set for this set is only 90 cards (which is 9 cards larger than the last couple 80th Anniversary team sets BBM has done - the 2015 Tigers and the 2016 Dragons sets). The 90 cards breaks down to 9 "Hawks History" cards, 48 cards of OB Hawks players and managers (and player-managers) and 33 cards of current Hawks players.
The "Hawks History" cards are odd for a couple reasons. The first is that they are numbered separately from the rest of the set - #HH1 to #HH9. The second odd thing is that instead of covering the entire range of the team's history, the subset only covers until 1968. I think but I don't know for sure that this has something to do with the Hawks legendary manager Kazuto Tsuruoka ending his 23 year tenure at the helm of the team that year. It would be the 50th anniversary of his stepping down this year. Each card covers anywhere from 1 to 7 years during this time. Each of the two years that Nankai won the Nippon Series during this period has a card to itself - like this one for 1959:
Ryan did a post about this set yesterday. You can see all the cards (including the insert sets) over at Jambalaya.