Well this item really challenged me because I wasn't certain what is was. Finally I came up with 1930s beachwear, sort of like 30s beach pajamas but short! So it's a 1930s romper and not a step-in as I originally thought. It is homemade white floral rayon and enhanced with pretty cotton pink voile. Two snap closures at either shoulder and a snap back sort of hanging belt. Cute cup style pockets with voile inserts. Voile also forms a yoke at and ends with teeny tiny buttons.

It's possible this was once a dress and someone made it into a romper . . .

Measures:
Bust 48''
waist 32''
hip 46''
inseam 1 1/2''
length 33''

condition: there are loads of frayed edges on the inside and one missing decorative button

This item is sold from a vintage boutique in Seattle.