Here is a great pre-worn black T-Shirt size LARGE that has a large graphic of a shamrock on the front of the shirt and says: CHICAGO IRISH Nothing on the back of the shirt.
The shirt measures 22 inches across the chest measured under the arms and from the back of the neck band to the bottom hem is 30 inches. The neck tag is missing, but I'll bet that this is 100% cotton and with these measurements it is a size LARGE.