Vintage 60s Seafoam Mint Green Gown - Sheer overdress may function with closure in front OR back (opposite) as shown. There are darts on closure side so probably worn toggle side on front by design.
Back nylon zipper. No materials indicated but feels like polyester for under dress. Dry clean indicated, I hand washed polyester under dress successfully.
No size tag fits like S, mannequin is 5'8" XS. See dress measurements and compare to similar nonstretch dress: 18" underarm to underarm, doubles to 36" max bust (mannequin is 32" bust), 15" across waist, 18" across hips, 53" long, 15" across shoulders, 19" sleeve from shoulder.
Nice condition - no flaws. Color is most true on majority of photos - where sleeveless underdress is shown color is too warm.

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