This blouse is such a gorgeous vintage find, I'd keep it for myself if I wore lolita more often ;u;
Made of a thin and lightweight cotton material that's perfect for summer, and it's decorated with lace that has flowers on it! 
The fit is quite loose on me (I typically wear a size S) so I think it looks nice under JSKs because that way the detail on the collar and sleeves stands out more
Has a general feeling of wear, since it is a vintage piece, but there are no noticeable flaws or pilling. Due to the simple design, I think it's a very versatile blouse that would go with a lot of different styles! 
Amateur measurements:
Bust: 40 inches
Waist: 36 inches
Sleeve length: 22.5 inches
Please let me know if you have any questions!