http://www.ebay.com/itm/281561398629
This vintage mackinaw was made in the 1930s. It is made of plaid wool, is double breasted, and has a pleated, belted back. The coat is lined in plaid flannel. It is missing half the buttons, with the other half having been moved to make the coat larger. These coats were popular as workwear and this example is heavily worn.

Chest (pit to pit, with buttons in correct position): 26″ (doubled = 52″)
Chest (pit to pit, with buttons in current position): 29-1/2″ (doubled = 59″)
Shoulder to shoulder: 20″
Sleeve (shoulder to cuff): 24″
Length (base of collar to hem): 31″