Cartoonmuseum Basel (that's the one in Switzerland) has an exhibit that, roughly translated, is titled "The Adventures of the Clean Line." The gallery show, which runs from October 26, 2013 through March 9, 2014, traces (no pun intended) the history of the "clean line"style of cartoon and comic art.
The above jam poster has examples of the clean line, with characters such as Tintin, Jiggs and others.
Oh -- there is, at that above link, a contest to see if you can name EVERYONE in this poster. But the deadline is midnight tonight (and I bet that means 6pm EST here in the States). I can't come close, myself.
Regardless, I want a poster of this!
Hat tip to Ulf K!