Here is a handsome vintage short sleeve collared shirt by Screen Mates. 50/50 poly and cotton blend, made in the USA. White shirt with rich maroon accents. Two button collar. Very light weight, thin, stupidly soft and comfy. It's in excellent shape with loads of life left. The tag says Large, but here are the measurements. (refer to the last pic above to see how I measure shirts)

Chest (armpit to armpit) 21"
Shoulder to end of sleeve (including cuff) 9"
Length 26"

This item is sold from a vintage boutique in Roanoke, VA.