Out the corner of your eye, this Chesterfield ad kind of looks like the work of Gil Elvgren. But, Elvgren's girls were always painted, but heavily photo-referenced, while this ad is a heavily retouched photo. Still, it's real pretty.
Elvgren, like most pinup artists, began each project with a photo shoot, setting up the model wearing non-specific clothing, but with the proper lighting. If her foot needed to be up on a tree stump or whatever, he'd use a chair. Props were inconsequential. They could be improvised in the painting, but the model had to be in the exact pose with the exact lighting. Anyway, Elvgren would then do a painting of the photograph, changing the wardrobe or props as he painted.
This Chesterfield ad is an airbrushed photo, meaning they made a big photographic print and airbrushed right on top of it. They tried to get that pinup "glow" out of the picture, but the real giveaway is the face and hands. There's a lot of the original photo left. You can see when you click through the picture and look really hard.
Also of note here is the fact that the artist had to paint the girl twice. It's easy to forget that when this ad was made in 1948, Photoshop was still science fiction. So, this was all done with paint brushes, X-Acto knives and contact cement.The artist had to combine two photos of this girl, basically painting her up twice. The Chesterfield logo was used to hide the seam where the two pictures meet in the middle.
I wouldn't want to paint the same head twice, even if it was just a matter of retouching a photograph. Let's see how similar they are.
Here's shot video of both heads, alternating. You can see that they are the same photo, but repainted twice. The brush strikes aren't the same. The hair is a little different, etc etc. Interesting.