Coat, British Warm (Officers). Private purchase from approved tailors, for use in barracks. Greatcoat (Officers Pattern) for use on formal parades and in the field. Major difference between the two, leather instead of Regimental buttons, Greatcoat has a belt at the rear and a British Warm is lined. No rank on British Warm. Greatcoat has a 2" collar that can be turned up against the weather and the lapels can be buttoned up to the chin. British Warm is made from cashmere, Greatcoat is made from heavy wool serge. Converted greatcoats are just that, a converted greatcoat and they look like it. A British Warm is a British Warm.