The poster is 20 x 38 1/2 unbacked.
Claes Oldenburg, born in 1929 was of Swedish origin but grew up in Chicago. He attended the Art Institute and moved to New York in 1956. He was associated with the Pop Art Movement and became known for his oversize sculptures of common objects.
Here is a lithograph poster from 1967 printed by Mourlot. It features a drawing of a Double Punching Bag. It was published by HKL Limited in an edition of 1,000 as part of the List poster art program
The poster is 20 x 38 1/2 and is unbacked.