Circa 1960s. Size XS.
The darling bow at the back...!!!!
This long formal gown features a wonderful diamond-textured fabric and is adorned with monochromatic 3D daisies all around.
 
Flat-Lay Dimensions:
Armpit to armpit - 22.5"
Bottom width - 25.5" 
Shoulder - 17"
Sleeve - 30"
Top to bottom - 34.25"