Original 1st printing 14 x 17" concert poster for the Grateful Dead appearing with the Flying Burrito Brothers (with Gram Parsons and Chris Hillman) and AUM at the Avalon Ballroom in San Francisco, CA from 4/4-6/1969.
Art by Jaxon (Jack Jackson), image is featured in the Art of Rock on page 111 (plate 2.25). Medium-thin glossy stock poster is in near mint (A-/B+) condition; aside from a small 1" hard diagonal bend in the lower right corner tip, a few stray handling dings/light pinch marks scattered around the image area and a couple of tiny edge tears in the right margin, it is a SUPERB example of this totally strange-looking Jaxon Grateful Dead image from the Soundproof Avalon series.
Check out the (professionally recorded) Burritos' set HERE:
https://www.youtube.com/watch?v=CVCAgBkMYrI&app=desktop