Its the old Marks and Spencer St Michael brand , Satin Rayon, Made in Italy. I would guess it was approx. 1975 vintage.
I also had this thin cotton shirt, approx. 1995 vintage, made in Macau, which had been hanging patiently and quietly in the other side of the wardrobe for at least 10 years.
I used a pattern to make a new top, using the scarf for the central panel and sleeves and the shirt for the other pieces.
The scarf even enjoyed a trip back home, to the rooftops of Milan cathedral.
More details and photos here