Built as Monassir for Khedivial Mail SS & Graving Dock Co Ltd, London. 1922 renamed Switzerland for Leith, Hull & Hamburg SP Co Ltd, London. 1928 renamed Duero for M.M. de Pinillos, Cadiz.
During the Spanish Civil war (1936 - 1939) renamed Urbi under Spanish Republican flag. 1939 returned to owner and renamed Duero.

1944 sold to Cia Maritima Frutera, Cadiz.
On 26 Jul, 1953, the Duero collided in dense fog with the British steam merchant Culrain (ex Empire Darwin), owned by South Georgia Co Ltd (manager Chr. Salvesen & Co, Leith), in the Strait of Gibraltar and sank within one hour in 35°37N/05°25W due to a hole in the #3 hold. No casualties among the 27 crew members and one passenger on board the Duero. The Culrain was only slight damaged and suffered no casualties. The survivors were picked up by the British ship and later transferred to HMS Daring. The ship was en route from Alicante to Las Palmas with general cargo, while the British ship was en passage from Middlesborough to Bone, Algeria.