Vintage St John Saks Fifth Avenue Navy Knit Sweater Style Dress in Size 8

Vintage St John Saks Fifth Avenue Navy Knit Sweater Style Dress. Knee length with a scoop style neck. Sleeveless dress in size 8. Made in the USA. The dress is in nice shape with no holes, rips etc. Not quite sure what it is made of as the tag is missing. It is a knit dress. Measures as follows laid flat, Bust, armpit to armpit, is about 20" Waist is about 18" on each side Length is about 401/2"