Reproduction '50s dress - medium

'50s style black and white 'polka dot insert' dress. Label states small but fits like a medium. it's a 36-in bust and a 27 to 30 in waist. No zipper, pull on. Measurements laying flat: armpit to armpit, 16 and a half in. Length of dress from shoulder to bottom hem is 40 and a half inches. Belt not included. Feels like polyester. Machine wash