You’ll see a “Hip-O-Potamus S.F.” on the bottom left of the shirt. That refers to an influential San Francisco company founded in 1970 by Jeffrey Axelrod and Barry Anderson. Their first job, after they had no luck selling their own designs, came when a store owner asked them to print out 200 t-shirts of an original design over the weekend. Says Jeff, who still sells some of the original Hippo Tees designs:
It just so happened that the owner of that very store was the wife of the drummer for the iconic band, the Grateful Dead. It was 1971 and she had the vision to sell t-shirts at rock concerts, and so our t-shirt venture exploded! Our first rock’n t-shirts [the company was originally called Rock-n-Roll t-shirts] went on tour with the Grateful Dead.
The company would later collaborate with promoter Bill Graham’s Winterland Productions, selling shirts at Bay Area rock shows, a practice that shortly became standard. Jeff (mushroom shirt) and Barry (far right) can be seen below, circa 1970.