It is a vintage POSH dress by Jay Anderson, most likely from the 60's.

I cannot find a size in the dress, so I have provided the measurements above.  In addition, the sleeves measure 23".   It is fully lined.  Has sheer sleeves and a sheer scarf.  There is also a slim sash that could bring in the waist.  The scarf could also be used as a belt if desired.

Zipper closure In the back.