Flat cap journal style boy guide the gazette of the gentleman as stated in Gentlemansgazette. Soft rounded and flat fabric, rounded edge. There are variations, both called flat caps.
Headgear in agreement with Ljmilitaria. Cap, boonie, cap, utility cover, garrison fatigue hat, cap, ranger hat.
Hat according to Wikipedia. Used headgear, including various weather protection conditions, reasons for graduation, religious security, fashion accessory.