Ever heard about the movie "Artists and models"?
It was released in 1937 and features some of the great illustrators of that time: Russell Patterson, Rube Goldberg, John LaGatta etc.
Checked my files and I found a promotional photo from that movie.
It features Peter Arno, Jack Benny (not an illustrator of course...) and McClelland Barclay, and is dated June 14, 1937. Enjoy!
While not beeing available on DVD yet TCM will show this in the US on February 23. And they have posted a few clips online! Including this one where we see Patterson and other artists drawing.
HERE are a few more clips.