Womens Ivory Silk Blouse

Gorgeous and classy dark ivory sleeveless top or shell. A little button at the top in back. Looks and feels like silk to me but there are no contents tags. There is no designer label either but there is a little tag with a 10 on it which I assume is the size. Do see measurements below though.
Excellent preowned condition. No issues to note.

Measurements laid flat and pulled taut.
armpit to armpit across bust all round: 42"
waist: 42"
length shoulder to bottom hem: 23"

Size: 10