Vintage 1970s lavender bridesmaid dress

Vintage from the 1970s. No tag (I think she’s handmade) but I’m thinking she’s polyester. Pictured on a size M but flexible sizing due to fully elasticized waist. Fabric has some stretch to it. Would fit sizes S-L. Zip closure at back. Hook and eye closure is missing eye. Have worn as a wedding guest dress, would also be a great prom dress! Bust - 18” (flat) Waist - 11-18” (flat) Length from shoulder - 57”