Original 1st printing 13&7/8 x 18&1/4" benefit concert poster for HALO (the Haight-Ashbury Legal Organization), held at Winterland in San Francisco, CA on 5/30/1967.
Poster lists appearances by the Grateful Dead, Jefferson Airplane, the Charlatans, Quicksilver Messenger Service and Big Brother & the Holding Company (featuring Janis Joplin).
Art by Rick Griffin, Stanley Mouse, and Alton Kelley, image is featured in the Art of Rock on page 193 (plate 2.206).
Medium flat index stock poster is in BEAUTIFUL near mint (A-) condition; aside from a tiny thin hairline bend along the upper right margin and a well-hidden pinch ding or two, this example is just about as sharp as they come.
For a closer look on which bands may or may not have participated in this event, read HERE: