Olive green wool Garrison Cap from World War I (a). There is a leather band around the inside of the cap and a darker tan lining. There is also a rainbow ribbon (b) for World War I Victory Medal on one side of the hat, this ribbon has three stars across it. On the other side of the front is a circular pin (c) that is engraved with "U.S. 9". The hat measures 4.5" (h) x 11" (l).
These caps are called garrison caps now, but back in WWI they were called Overseas cap.
Note: This was recommended for the permanent collection by Megan Huelman on 10/6/2013.