Genuine OD jeep cap.  This is the Cap, Wool, Knit, M-1941.  An OD knitted wool cap with a small bill sewn in and the sides can be turned down over your ears for warmth.  It can also be worn under the helmet in cold weather.  Most GIs loved this cap and General Patton hated because he thought it looked unmilitary.

This is GSA compliant, made in USA.  It's too dark and too big for authentic reenacting, but it's a good warm cap.