Tower Of Power Concert Poster Oakland 2018 Artist Proof. Tower Of Power Concert Poster. June 1 -2, 2018. 15 3/4? X 24? Designed & Signed by Chris Peterson. Numbered Artist Proof by Chris Peterson. What is an Artist’s Proof? An Artist’s Proof is an old tradition of reserving a quantity of prints for the artist’s use, printed at the same time as the regular edition without changes. In the early days of printing, these prints were the only remuneration the poor artist received. We have a few of these in stock, you may receive a different # then what is in the photo. At visiblevibrations, we only sell ORIGINAL Concert Posters, Art Prints, Music Memorabilia and Limited Edition Art Toys!