The shirt looks like a vintage 60's Pendleton Woolen Mills to me.
I agree with Mr. Atoz. Pendleton.
This is not the red version, but an olive/black version ("Buffalo" pattern).
The closest color I could find is the red/blue Ombre.
READ AND FOLLOW CARE DIRECTIONS CAREFULLY! I received one of their shirts as an Xmas gift and washed it. It shrank!
--Paul E Musselman