Original 1st printing 13&1/4 x 18&7/8" early 1967 fan club promotional poster for the Grateful Dead.
Art by Stanley Mouse and Alton Kelley with photos by Herb Greene, image ("The Golden Road to Unlimited Devotion") is featured in the Art of Rock book on page 187 (plate 2.192)- this is the no white border/smaller machine-cut version.
Medium-thick flat vellum stock poster is in good to very good (B to B/B+) condition; a small dime-sized oil stain in the lower left corner, a tiny set of pin holes, a tiny chip on the "n" of "Unlimited", a hint of surface wear and a stray pinch/stress crease or two, otherwise fine.
An overall very decent example of this early '67 Mouse & Kelley Grateful Dead image. Here's a killer Winterland show (BG 55, if you're curious) from right around when this poster came out;