This dress is really lovely and I adore the fabric. As Linn stated, a burn test will reveal if it is silk. In one photo it looks like a silk taffeta, but in another it almost looks like a fine silk faille. Really nice.
I get a strong sense of late 1930s from the fabric, the colors and the pattern, but not so much the silhouette. I am wondering if this has been altered, updated after WWII. Can you tell if the pink velvet ribbon was an addition? The ribbon looks like antique silk velvet to me. Can you show us the stitching inside where the ribbon as been sewn on?
Also, has the hem been altered at all? Could this have been a full length gown and has been made shorter?
What a great thing to find at a thrift shop!