This was the designation of Allied tanker and troopship convoys (together with a numerical suffix) plying the route from French North Africa or Dakar, French West Africa, to Aruba or Curaçao, Dutch West Indies, and as such reciprocals of the 'OT' (iii) series (February/October 1943).
The first of these convoys was TO.1 of 24 February/6 March 1943 with four US tankers in the form of the 11,355-ton America Sun, 10,172-ton Cherry Valley, 10,169-ton Esso Norfolk, 10,172-ton Esso Washington and the 23,788-ton troopship George Washington. The last was TO.14 of 20/31 May 1943 with five US vessels in the form of the 9,879-ton Dartmouth, Esso New Haven, 10,195-ton Lookout Mountain, 9,879-ton Occidental and 9,910-ton Sachem.
A subvariant was the convoy route from Curaçao to New York City, these convoys starting with TO.4A of 23/28 May 1943 with six vessels including three US vessels in the form of the 10,180-ton Cornell, 10,342-ton Seakay and 10,804-ton Sheldon Clark, and ending with TO.9A of 24/29 October 1943 with four US vessels in the form of the 10,198-ton Buena Vista, 11,237-ton Esso Little Rock, 10,172-ton Esso Washington and 10,169-ton Vera Cruz.
An oddity in this sequence was TO.15 from Mediterranean ports to New York City on 3/15 July 1944 with 10 US vessels in the form of the 10,195-ton Crown Point, Duquesne, 9,887-ton Esso Hartford, 10,317-ton Esso Portland, 10,169-ton Esso Wilmington, 10,296-ton Lyons Creek, 10,195-ton Perryville, 10,195-ton Spotsylvania, 10,317-ton White Horse and 10,172-ton Wood Lake.