I'm not sure when exactly this pictures where made, but to my guess it could be late 1940s or early 1950s.
Look at the second picture, where the base pattern of the top is clearly visible. So easy!
I will certainly try this with a piece of cotton knit fabric, but I'm sure any other lightweight fabric will do.
To close the front panel, just add two thin bindings, to close the back panel in the front, sew-on a wider binding made of the same material, long enough to make a bow.
Super-easy and so nice for warm summer days!