Super cute and unique half slip by Vassarette. I have never seen one like this. It doesn't have elastic all the way around the waist,
only in the back. The front is just flat. Then it has these two triangular shaped inserts on the back side. Why? I don't really know, but I do know that this is super cute, and probably can be worn as a skirt as well. Label says 100% Antron Hem is also different than most slips. No lace, the hem is rolled.
It's some kind of nylon tricot material Fabric has a bit of a sheen to it and seems stiffer than regular nylon. It holds it's shape. It is a little bit sheer but not much. Label also says size A Large.

Excellent condition, size L (10 - 12) and M (6 - 8).

Detailed measurements:

Waist - 26 inches unstretched - up to 32" stretched.
Hip - 38 inches
Length - 24 inches.

This item is sold from a vintage boutique in Ames, IA.