1920s Baby Pink Silk and Lace Step-In Lingerie Shorts Pants .
Sewn like a skirt with an insert between the legs (I don't know how to describe it accurately - English is not my native language).
As shown, untagged ,maker unknown. Possibly handmade . Perfect work -the best possible. I would call this work jewelry. The highest quality silk and lace.In the photo, I put a pin next to the button to show how tiny they are.

Measurements: waist 12 1/2"/32 cm
length from waist to the edge: 17"/ 43 cm
across seat/hip 21"/52 cm lying flat

Excellent antique condition! I don't see any signs of use, but you still have to remember that the thing is about 100 years old.