This is Eugene's tunic/jacket from World War I. It's made of wool (very scratchy!) and lined with cotton.
Several years ago, a WWI expert looked at the jacket and had this to say about it:
The tunic was probably custom-made, not standard issue. The tag inside doesn't give indication of where it was made. It's also very small (Eugene was only 5'7"). It fits me, as you see below, and I'm 5'1".
Collar detail. The collar insignia is for the artillery corp, D Battery.
The left sleeve has several patches.
The bomb insignia identifies a member of the Trench Mortar section.
The red chevron is for his rank, private 1st class, and the red is for an honorable discharge.
The double chevron indicates one year of overseas combat-- 6 months for each stripe.