Vintage Silk & Lace Black Button Up Nightgown Size undefined

Vintage Back button up nightgown Feels like silk but I can't be sure because there are no tags Lace trim on neckline and at elbows 3/4 sleeves Semi sheer Good used condition A large based on how it fits my mannequin but please read measurements carefully Measurements (flat lay and approximate) Shoulder: 16 inches Arm: 15 inches Bust: 20 inches Waist: 20 inches Length: 39 inches