Pelons are extremely rare "practice pieces" for the early t-shirt designs. Before production was initiated, the image or design was tested on cotton cloth or burlap to determine the color and line accuracy of the piece. Only a few of the "tests" were preserved once the design was deemed acceptable and the t-shirt went into production.
Bill Graham's Day on the Green concerts were the first prototypes of "festival" shows - multi performer sets in stadium settings. Staged on the lawn of the Oakland Coliseum, the Day on the Green concerts were a summer series started in 1973 that continued until shortly after Graham's death in 1991.