Vintage Evan-Picone Blouse, Brown and White Floral Print Blouse Size Small, (poss medium). 
This is a gorgeous 1970s era blouse in a brown and white abstract floral print.  Long sleeve, elongated collar, and a straight hem so it may be worn untucked.  
There is no fiber content tag, but this feels like a very soft and thin cotton.  Not quite gauze, but feels like a tissue cotton but isn't sheer.  So lovely!
Marked size 12, but model wears a modern womens size 6.  Based on measurements, this seems best for a womens small or 6, but could possibly accommodate an 8. For best fit, please compare the measurements below to your own, or to the size chart of a brand that fits you well. 

Bust: 38"
Waist: 34"
Across shoulders: 15"
Shoulder to hem: 27"
Armpit to cuff: 18"