Vintage Silk and Lace Slip - Slip Dress - Chemise

I purchased this at a Toronto consignment shop, sold to me as silk and lace. For vintage condition, it’s immaculate. The straps are fixed and it can be worn with the pin tucks in front or back, with one lace neckline slightly higher than the other. The sizing is flexible - could be x-small/small/medium. I’ve never worn this. It does have some slight discolouration under the arms, I just haven’t tried to get it out. Laying flat: almost 18” pit to pit / waist, width of slip is approx. 18” as well. // length from front neckline with pin tucks: 29 1/4”