Barbizon "Saucy" fancy white slip in their patented fabric "Tafredda" which feels like a lightweight taffeta.  The front of the bodice is lace over a solid layer of "tafredda".  It is pure white despite appearing ivory in some of the images.

Features a side zipper and 6" lace edged side slits at the base.  I would date this piece late 60s/early 70s since the zipper is a talon.   It is in new condition, looks as if it were folded in a drawer and never worn.  Vintage sized at a 14 but more accurately measures a small.