Old field gray wool mountaineering or hunting hat with ear flaps and neck guard that fold up and secure with buttons. This is a World War Two period hat and may be marked 1941 on the lining (please see the photos).
It measures about 20" around. It does have some spotting / surface soil.
It is from an estate near New Glarus, Wisconsin, also known as -Little Switzerland-. We're not sure if this cap is an American piece or it may have been brought back from Europe.