United Kingdom
 
British “Royal Scots Dragoon Guards” cap
Also nicknamed the “Carabiniers and Greys,” the Royal Scots Dragoon Guards forms part of the British Army’s “Royal Armoured Corps.” This distinctive hat is one of the most colorful of the current U.K. caps. The distinctive band is called a "Van Dyke" and has been used by the Scots Greys since the beginning of the 19th century on forage caps. It was white until the 1840s at which time it became yellow, which was the facing color of the old 3rd Carabiniers Regiment. The Royal Scots Dragoon Guards were formed from the Royal Scots Greys and the 3rd (Carabiniers) and 6th Dragoon Guards. Many thanks to Cédric for filling in the historical details.