The psychedelic art by Zap Comix team Victor Moscoso and Rick Griffin features a large scarab beetle holding up sun orb while six legged yin yang symbols frolic underneath. (Iconic lettering by Griffin, scarab by Moscoso). This poster obviously is looking to find a home for it’s twin, BG-141, as well. That poster is called Iron Butterfly Trash Burner (don't ask) and you can find it on this website under "Other bands of the Psychedelic era."
These 1968 concerts at Winterland, a former ice skating rink, featured The Jimi Hendrix Experience, Buddy Miles Express and former/future Quicksilver Messenger Service singer Dino Valenti as the opening act. Bill Graham used Winterland for bigger acts which, by 1968, Hendrix certainly was. Winterland held about 5,000 people versus the Fillmore and the Fillmore West which both held between 2,000 and 3,000 depending on how many people Graham could squeeze in that night. Both concert venues were open-floor ballroom style where people could (and would) dance.