his blog is fantastic-- he's a talented illustrator who shares images from the golden age of American print advertising.
Here's one with a geologic puzzle. Real rock or not? Not my field, but I'm guessing not, but only because this painting was very carefully composed and I think the illustrator made the rock fit the image. Maybe it's the most famous rock in Canada, guarded day and night by Mounties. I hope not.
Leif's original post here.