Vintage Maxi Dress 60s/70s mod hostess psychedelic floral Puritan Forever Young

Lovely iconic maxi/hostess long dress in stunning a psychedelic/mod print.  Top is a very dark navy blue with an attractive notched neckline.  Empire type waist.  Tags inside with the brand PURITAN FOREVER YOUNG and a fabric care tag.  I don't see a size tag.  Measurements are below - appears to be a small/medium size. In one of the photos, you can see a little 3 on the back of the fabric care tag, but I don't think it relates to the size. Measurements: Approx 18 inches across underarm to underarm, approx 14 inches across waist, approx 20 inches across hips and approx 56 inches measured from neckline down the back to the hem.