Some artists felt that ad work was beneath them. But Coles Phillips began to change this. He was proud of whatever art he produced and the advertisers were proud to have him. Today, we call this "synergy." For those who wanted Phillips' artwork, it was just common sense. His watercolors of beautiful women moved merchandise. Most other illustrators followed Phillips' lead. Haddon Sundblom signed some ads, but for his own reasons never signed the lush ads for Cashmere Bouquet.
But signing one's artwork and having that signature making it into print is another thing. Artwork was often cropped, sometimes a lot, to make an illustration fit new or "improved" ad specs. If the signature got the crop, who cared? It was an ad, for cryin' out loud, not Da Vinci. Sometimes an advertiser would tout that a beautiful print could be purchased directly, though who painted the art for said print, they forgot to mention.
Finally, a signature, even left in its place and escaping the x-acto, wasn't necessarily readable after all the steps it went through to make it to the readers' hands. Sometimes the registration was so off, the ink overruns so thick, or the illustration so reduced (and often all three), that the signature lives on only as a squiggly smear.
What are we up against?
First, there's the artist who seems to have never signed his work. There are dozens of beautiful Union Carbide ads featuring strong hands. Someone knows who that artist is. I need to hear from you. And if they don't sign, it's hard to guess. Am I looking at an Elvgren or a Loomis or a Harris, or a Buell? Sometimes artists expect you to know them by just one name. That's fine if it's "PAUS," but what if they only sign it "Johnson." There are at least 100 artists who are listed and have the last name of "Johnson." Thanks. Some brush jockeys don't so much sign as leave a mark (Edward Penfield and J C Leyendecker come to mind) or leave but a few initials. Yes, "AS" is Arthur Sarnoff, but "CP" isn't necessarily Coles Phillips; more likely Clara Elsene Peck. And what about the wise guy who just leaves a single letter, like "F" (I'm on to you Robert Fawcett).