Original 1st printing 14&1/4 x 20" concert poster for Quicksilver Messenger Service appearing with Mount Rushmore from 6/29-30/1967 and Big Brother and the Holding Company (featuring Janis Joplin) appearing with Blue Cheer from 7/1-2/1967, all shows held at the Avalon Ballroom in San Francisco, CA.
 
 Art by Victor Moscoso, image is # 68 in the Family Dog/Avalon series. 
 
Medium flat index stock poster is in near mint (A-) condition; aside from the TINIEST of pressure creases in the bottom left corner tip, this is an essentially-clean/unimprovable 1st printing example of this mind-boggling Moscoso Avalon poster from mid-1967.