These were probably from a pack of souvenir cards, from the 1940's. Because the girls are topless, a serviceman may have removed them from the pack, before sending it home! They are an accurate depiction of life in old Hawaii. They measure 2&1/2 by 3&1/2 inches, and are in excellent condition, with no marks, or yellowing. Minor corner ding on one card.
I have 125+ pieces of vintage Hawaiiana in my shop, including other ephemera, and am happy to combine shipping. You can see them all by typing the word, "Hawaiian" in the search box at the top of this page.