Original 1st printing 22&1/2 x 17&1/2" legal defense benefit concert poster for Quicksilver Messenger Service appearing with Robert Savage (A.B. Skhy and Beggars Opera both canceled) at the Frost Amphitheater on the campus of Stanford University in Palo Alto, CA on 8/9/1970.
Artist unknown/not credited, medium flat index stock poster is in very good to excellent (B/B+ to B+) condition; there is a bit of smudging/dirt along the left side of the image area, presumably from the press (it is printed into the image doesn't extend into the white area of the left border), along with a series of very thin vertical stress bends hiding within the image area (mostly visible from the reverse), a thin corner bend or two and a few stray light handling dings here and there, otherwise fine.
Very cool low-run Quicksilver item from Palo Alto, check out a first-hand account of the show (with photos!) HERE;
http://cryptdev.blogspot.com/2011/10/frost-1970-country-joe-and-quicksilver.html