Chamber Brothers at the Avalon Ballroom (Family Dog Productions, 1967) Concert Poster by Victor Moscoso - This 1967 concert poster, illustrated by Victor Moscoso, advertises an appearance by Chamber Brothers and Iron Butterfly at the Avalon Ballroom on April 28th and 29th, 1967. This is a first printing, identified by the white gap on the inside of the bend in the thin bright pink border directly to the right of the eye of the woman on the right (this space is not seen on the reprint). Measurements: 14 x 20 inches.