The 13-point lightning bolt was derived from a stencil Owsley Bear(along with his close friend Bob Thomas)created to spray-paint on the Grateful Dead's equipment. Owsley was an underground lsd cook/ longtime soundman and financier for the dead)
The Dead in those days had to play in a lot of festival style shows where the equipment would all wind up at the back of the stage in a muddle, it was created to help the crew find the Dead's equipment in the jumble of multiple bands' identical black equipment boxes at festivals.
The lightning bolt design came to him after seeing a similar design on a roadside advertisement: "One day in the rain, I looked out the side and saw a sign along the freeway which was a circle with a white bar across it, the top of the circle was orange and the bottom blue. I couldn't read the name of the firm, and so was just looking at the shape. A thought occurred to me: if the orange were red and the bar across were a lightning bolt cutting across at an angle, then we would have a very nice, unique and highly identifiable mark to put on the equipment."