This full-page ad features a pretty nice illustration by Nick Carter. His signature is in the lower left. I'd never heard of him, but that doesn't mean he's not famous. All I could find were more ads for Petri wine, all of which seemed to be pretty similar to this one, with some kind of highly rendered cartoon character.
Petri wine was a sponsor of the Sherlock Holmes radio program, which ran from 1939 to 1947. This as is from the post-Holmes days, but it looks like Petri were still doing well, because full color full page ads in Life magazine couldn't have been cheap. The curious can download free MP3s of the show (and loads of others) from Archive.org.
Rendering cartoon characters realistically brings up some weird problems. Most obviously, when you render up a cartoon character as if it were a real-life thing, it can look creepy. The giant, staring eyes and generally bulbous proportions of most cartoon characters would be downright unsettling if you encountered them walking down the street. You know... like the freaky Alvin and the Chipmunks movie, Garfield, or Scooby-Doo movies? Those things make my skin crawl like it's trying to get off. I've run into this problem a bunch of times when I've been asked to render up a line drawing of a character as if it were a real thing. Once you start shading, airbrushing or lighting a cartoon, you are eyeballs-deep in the uncanny valley. Make a cartoon real, and you've got a crime against nature whose every breath must be a hellish torment of broken anatomy. "kiiillll meeeeee" they seem to groan.
This beaver's pretty nice, though. Carter's done some great work rendering the fur.Fur is as pain to paint. You don't want to just paint every hair individually, but you can't just spray it with a huge airbrush or it'll look like it's molded plastic. You pretty much need to make it blotchy but soft, like you see here. Lots of variations of your base fur color blending into each other.
I don't think Carter had any formal cartoon training (Yes, there is such a thing.), though. There are some mistakes in the structure of the beaver that none of my cartoon buddies would have left alone.
For hands, you can usually get a really good start just by drawing a mitten and then adding some finger divisions. From there, you can refine it, depending on the needs of the illustration, but for cartoon characters you can almost always leave it there. It may take a few attempts to get it right, but this wil generally be better than the inexplicable "finger fan" that so many people seem to like drawing.
Second, I would have brought the lip line up into the cheek, instead of leaving the strange no-man's land between the two. Cartoon characters look happier this way. I think Carter was using his own human (probably) face as reference, and that's not always best for cute cartoon characters.
If I had to guess, I'd say that Carter probably started with a photograph of a person in the beaver's pose, and sketched over it. This leaves the cartoon character looking like a person in a costume, and limits the character to the constraints of existing human proportion. This is a standard operating assumption for illustrators. However, cartoon characters are often big squishy bag shapes, with stumpy legs.
I still like it, though.