Baby Outfit Mid Century "wee Togs" With Gift Box

Vintage mid century shirt and diaper cover set with gift box. States size med but looks approx. age 6 mths. Has never been out of the box until today and no signs of wear to the outfit. Box has a crease/tear in one spot. The fabric is unusual-I'm going to guess its acetate or similar thin shiny material. The diaper cover is lined with plastic. Colors are yellow and white. Part of a wonderful collection of vintage items from an estate now on consignment.  From non smoking home stored in plastic. (TH)