9.5x12" sheet of animation paper has lead pencil image areas w/figure of Mickey Mouse shown from the waist up w/arms extended and mallets in air. Attributed to Ub Iwerks. Image measures 3.25x3.75" long w/number "325" at lower right corner. Back of sheet has stamped "320" number at upper right. From scene six minutes into the cartoon where Mickey uses mallets to play bull's teeth like a musical instrument. Sheet has even lt. aging. Scattered corner tip wear, but image areas remain clean and Exc. Nice image from sequence. Released on Nov. 18, 1928, "Steamboat Willie" was the third Mickey Mouse cartoon to be produced, but was the first to be distributed and the first to be shown. It is historically recognized as the first cartoon to feature a fully post-produced soundtrack. Historic Disney animation art.