This looks absolutely beautiful on. Could be worn any number of ways - as a dress (with a slip dress undernearth), as a sleeveless jacket or a tunic over culottes/ trousers.
It is much more fitted when on than the photos suggest... so when tied sits fitted to the body.
I can't find a size or fabric label but I'd say it would be a good fit on a UK12 - UK14. Sits a couple of inches above the knee (based on a height of 5'7").
And it is almost certainly made from a thick-weave cotton.
In immaculate condition.