In EMP's description, they also say that it
appears to be a proof. They go on and add:
"We know nothing more about the poster, but it is certainly interesting and different! If anyone knows more about this, please e-mail us and we will post it here."Just a thought: Maybe it was a copy that was taken off the line, by a print worker, prior to the last pass of inks, (and the printer's info was likely printed in black) because that person liked the way it looked in those more eerie, light green tones? (Similar to how some posters from the '30s thru the '70s, for example, have shown up, never folded, because someone snagged them before they reached the folding part of the line).
Just a guess, but in any case, it gives it a very different, overall feel.