This is a WWI army issue pullover wool shirt. It has two breast pockets, one with stitching for a pen. The sleeves have reinforcements at the shoulders. The original tag is still at the hem, but it is mostly illegible. The chest and placket are partially lined. There are gussets at the tails.
Chest (pit to pit): 24-1/2″ (doubled = 49″)
Shoulder to shoulder: 18″
Sleeve (shoulder to cuff): 23-1/2″