As the 1974 season progressed, 35-year old Lou Brock was the toast of baseball because he was threatening Maury Wills' single-season stolen base record of 104, set in 1962. This feat inspired a group who wore these t-shirts, one of which you can now buy for about a dollar for every base Brock stole in his career.
1970s t-shirts are delicate things. We should be amazed that any of them survived the century, what with hard water, harsh detergents and ultra-strong deodorants degrading their structural integrity. Whether or not you shell out a mortgage payment for this item, at least be happy it still exists!