1955. The boob shelf is a very mid-50s design element. Where it hits the breasts (underneath or partway up), the angle to the shoulders, and whether it is flat or dimensional (as well as sleeve treatment) are all key points to resolve for your own proportions if recreating this element.
Prom, 1969. My mum has an ALMOST IDENTICAL pic of herself from this era, with the same amazing, ornate hair, wearing her candy-pink chiffon Marie Antoinette-style evening dress that looks a bit like the lady's on far right, but it has lace cap sleeves, and lace and crystals (my mum was annoyed I called them 'sequins' in the book) decorating the bodice.