Original 1st printing 14&1/4 x 20" concert poster for the Youngbloods with the Sparrow (proto-Steppenwolf) and the Sons of Champlin at the Avalon Ballroom in San Francisco, CA on 12/16-17/1966. Art by Stanley Mouse and Alton Kelley, image is # 39 in the Family Dog/Avalon series. This version (OP-4 in Eric King's book) is a fairly recently-discovered (2003) variant/proof that is missing the black pass of ink and has an additional 1/4" white border on the right margin. Medium-thick flat vellum stock poster is in excellent (B+) condition; a set of tiny pin holes (top two corners), a hint of handling wear, a tiny black ink mark on the warrior's chest and there is a bit of off-register blue ink smearing on the right margin, but otherwise it's a great-looking example of this unusual-looking early Family Dog poster.