The Glengarry is the same color as the army’s service dress uniform with a black band and two black swallow-tail ribbons at the rear. The cap badge is worn over the left eye. … Army pipers and drummers wear a black Glengarry with a saffron band and ribbons and a dark green feather hackle.
The Glengarry hat is a traditional Scots cap made of thick-milled woolen material, decorated with a cookie on top, frequently a rosette cockade on the left side, and ribbons hanging behind. It is normally worn as part of Scottish military or civilian Highland dress, either formal or informal, as an alternative to the Balmoral bonnet or tam o’ shanter.
Traditionally, the Glengarry bonnet is said to have first appeared as the headdress of the Glengarry Fencibles when they were formed in 1794 by Alexander Ranaldson MacDonell of Glengarry, of Clan MacDonell of Glengarry. MacDonell, therefore, is sometimes said to have invented the Glengarry – but it is not clear whether early pictures of civilians or fencible infantry show a true Glengarry, capable of being folded flat or the standard military bonnet of the period merely ‘cocked’ into a more ‘fore-and-aft’ shape. The first use of the classic, military Glengarry may not have been until 1841 when it is said to have been introduced for the pipers of the 79th Foot by the commanding officer, Lieutenant Colonel Lauderdale Maule.
It was only in the 1850s that the Glengarry became characteristic undress headgear of the Scottish regiments of the British Army. By 1860, the Glengarry without a diced border and usually with a feather had been adopted by pipers in all regiments except the 42nd (Black Watch), whose pipers wore the full dress feather bonnet. In 1914, all Scottish infantry regiments were wearing dark blue Glengarries in non-ceremonial orders of dress, except for the Cameronians (Scottish Rifles) who wore them in rifle green, and the Scots Guards, who wore peaked forage caps or khaki service dress caps.
The diced bands on Glengarries were either in red, white, and blue for royal regiments or red, white and green for others. The theories on top could be red, royal blue, or black, according to the regiment. The Black Watch and Queen’s Own Cameron Highlanders, however, wore Glengarries without dicing and The 93rd (Sutherland)Highlanders were unique in wearing a simple red and white chequer pattern. This was said to commemorate the stand of the 93rd Sutherland Highlanders at the Battle of Balaclava immortalized as The Thin Red Line.
Between 1868 and 1897, the Glengarry was also worn as an undress cap for most British soldiers until replaced by the short-lived Field Service Cap. When this was revived in 1937, the Dress Regulations for the Army described the Universal Pattern Field Service Cap (used by the British Army in World War II) as “similar in shape to the Glengarry.”