The closeup of the hostess doing card tricks as the deck is shuffled shows a slender male's forearms and hands, clearly not the less muscular hands and wrists of the actress portraying the hostess.
Although the story takes place in 1941-1942, all the women's fashions are from 1956.
The ship Mamie boards at the beginning is the S.S. Hawaiian Packer, which was launched in 1943. However, at one point in the Bungalow Club, she is reading a newspaper with headlines about the Battle of Midway, which was in June 1942.
The red convertible that Jim drives is a 1946 model.
This movie is set in the early 1940s, but Joan Leslie is wearing a mid-1950s hairstyle. To see how she really wore her hair in the early 1940s, check out Hollywood Canteen (1944).