Nice Vintage Condition! This is a vintage medium, which is more like a modern small. Please see the measurements. There is a logo on the arm sleeve. There is a small light streak in the front. Material is piled in some areas. Please see the photos and measurements below.

When laying flat, armpit to armpit measures 19 inches. 
When laying flat, shoulder seam to the bottom of the arm-sleeve measures 10.5 inches. 
When laying flat, shoulder seam to shoulder seam measures 17 inches. 
The measurement from the back/middle collar seam to the bottom of the shirt is 29 inches.  
This shirt is in nice vintage condition and comes from a smoke-free home.  Thanks for looking!