Vintage polka dot halter maxi dress

No fabric tag, best guess is poly or poly blend, no stretch, navy blue and white polka dot pattern, halter style neck with ties, fitted waist, zipper in back, maxi length, vintage, mid 70’s, very retro, pinup girl style, JC Penney, size M, measured flat app: pits 19”, waist 17”, waist to hem length 42”, not sure if that MW is actually the size but the measurements indicate a M, very good condition (T-83)