This feels like nylon crepelon.

Label reads - "Pembrooke" - 36 - 100% Nylon - Exclusive of Decoration - Size 36 - RN 15084.

Measures - 40½" around inside of bust - 39½" hips - 31" in length from top of shoulders.

Satin shoulder straps with metal sliders connected to slip in 2 places - bust darts from side seams - seam from top to below hips in back - very good condition, no flaws found.