This is a classic vintage Madras plaid shirt, made in India. Popular when I was a kid (I remember being fascinated with the ring at the center back yoke, lol) it's still a lightweight summer wardrobe staple many years later. Referred to as 'bleeding Madras' because the fabric dye colors were not stable, and prone to run into each other, it's a lightweight cotton broadcloth. This shirt is short sleeve with a perfectly matched pocket on the left chest, a button collar and button front. Yoked in back with the requisite fabric loop. 
 
Pre-owned, used. In terrific condition. Machine laundered and line dried, I didn't notice any color run. 
 
Marked as size M or medium- PLEASE READ this shirt's measurements given next--
Pit to pit- 21 1/2" across the front
Hem- 42"
Center front length- 26 1/4"
Sleeve length- 1 3/4"
Back width- 18 1/2" across the base of the yoke