This is such a pretty gown from the 70's by JC Pennys. Two piece style. You could actually use the top to wear as a blouse on its own. The under dress is a straight neckline style with spaghetti straps. Chiffon over the base polyester fabric. Elastic across the top of the back. The blouse is sheer with lace insets. Elastic waist with a lace peplum. Full sleeves. It has a wide ribbon sash. There is a rust mark on the ribbon that I did try to get out with no success. I would ditch the sash all together or easy enough to replace at your fabric store. All in all this is a beautiful gown in excellent condition. Best fit would be a Medium, however, please see the measurements for a proper fit.
Measurements
Dress
Bust 36"
Waist 26"
Hip 44"
Length from top of back 47"
Length from waist 42"

Top
Armpit-armpit doubled 40"
Waist 22"-34"

This item is sold from an excellent, highly rated vintage boutique in Westfield, Massachusetts.