In addition to Jerry Siegel's barrage of letters sent directly to National Comics executives regarding his anger over the $130 sale of the rights to Superman, he also contacted many of his former contemporaries including Joe Simon and Jack Kirby who were working at Crestwood Publishing at the time.
In response, Simon and Kirby wrote this signed letter of support to National Comics publisher Jack Liebowitz indicating that Siegel's opinions are "certainly not shared by any of the old D.C. crowd." They also mention Liebowitz's fair treatment of creators during World War II, though it's worth noting that Siegel was deployed in Hawaii when he first learned that National had published a Superboy story, based on one that he had submitted but was not purchased. Additionally, it is somewhat ironic to see Kirby sign a letter in support of a publisher during a feud with a creator as he would have his own troubles with Marvel a few decades later.
Letter is in good condition with some minor staining at the bottom. 7 1/4" x 10 1/2".