Authentic 1940s vintage clothes are always a treat to find! With severe fabric shortages as a result of the war, which lasted through the whole decade, clothes were made with a minimum of fabric, few pleats and limited decorative embellishments. Skirts were just below the knee, trousers were even more popular for women and jackets were boxy with broad padded shoulders.
From 1942 onwards some clothing was made under the government utility scheme that rationed materials and can be identified with the CC41, Civilian Clothing Act of 1941, stamp or label. The rare the double eleven (IIOII) label was used in very limited amounts and was added to garments that were made without rationing restrictions, it is exceptionally rare to find clothing with this label in it.
1947 Christian Dior introduced his "New Look" which revolutionised 1940s fashion as it was everything that rationed clothing wasn't, fuller long skirts, dropped shoulders on jackets and cinched in waists to emphasis the amount of fabrics being used. This iconic look of course travelled in the 1950s and is often more associated with that decade.