Unknown size and materials. 
Fits like an XL or XXL based on measurements. Please measure against a favorite shirt to ensure accurate fit. 
Feels like a polyester rayon blend, super soft. 

Approximate measurements lying flat:

Armpit to armpit 25"
Length 23.5"
Shoulder to shoulder 12.5"

Fabric has a lot of stretch an open under arms giving some flexibility on sizing.