It was made by Health-tex Stantogs and is marked a size 3T. It appears to run smaller, more like a size 18-24 months but please refer to my measurements below to ensure proper fit. It seems to be a short-waisted style.
It is made of a soft and stretchy knit fabric, probably a cotton/poly blend. it is in great vintage condition with no flaws to note.
Length (shoulder to bottom)- 11.25"
Underarm to underarm- 11.25"
Shoulder to shoulder- 10"