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South Durham Steel and Iron Co of Cargo Fleet Ironworks, Middlesbrough
1860 A predecessor company was opened as a malleable iron works - Stockton Malleable Iron Works
In 1898 Christopher Furness, in association with Mr. W. C. Gray, of West Hartlepool, purchased the Moor Steel and Iron Works, of Stockton-on-Tees, the Stockton Malleable Iron Works, and the West Hartlepool Steel and Iron Co, which were converted into a single undertaking, the South Durham Steel and Iron Co (Limited).
1898 Public company. The company was registered on 29 December, to acquire certain properties, but they were carried on practically as a private undertaking until early 1900. 
1903 'THE BURSTING OF A FLY-WHEEL. An inquest was held at West Hartlepool yesterday on the three youths — Joseph Callaghan, Robert Samuel Smith, and Ernest William Wilson—who wore fatally injured by the bursting of a fly-wheel at the local works of the South Durham Steel and Iron Company. Mr. Henry Crowe, chief engineer to the company, expressed the opinion that the cause of the accident was that the engine was allowed to get up an excessive speed owing to the governor becoming inoperative, because of the key which coupled the shaft and the wheel together having come out. This key was found lying on the ground beside the governor the day after the accident At the time when the accident happened the engine had practically no load on it. After hearing a number of witnesses, the jury returned a verdict that the deceased were killed accidentally. They ascribed the bursting of the fly-wheel to the governor-wheel being defective, (1) through the wheel being bushed, and (2) because the keyway was not deep enough in the wheel and shaft. The jury expressed their appreciation of the services of Police-Constable Parker in rendering first-aid to the injured. 
1905 'A THOUSAND MEN IDLE. The bursting of fly-wheel at the Moor Works, Stockton, of the South Durham Steel and Iron Company, Limited. Nearly a thousand men are laid idle. One was injured, though in a similar accident at the West Hartlepool works of the same company some time ago two men were killed.'
1906 To year end 30th September the output was 353,000 tons of finished material.
1914 Directory: Steel Manufacturers of Stockton. 
1927 See Aberconway for information on the company and its history.
1937 Steel manufacturers. 
1955 Public offer for sale of shares in South Durham Steel and Iron Co by Holding and Realisation Agency.
1961 Iron and steel manufacturers, constructional engineers and mine owners. Products include: ship, boiler, plain, high and low tensile, special qualities and flooring (Dunbar and diamond patterns) steel plates, welded steel pipes, welded and pressed tanks, steel masts and derricks, fabricated steelwork, steel sections, joists, rails, fishplates, broad flange beams, larssen steel piling, "Rendhex" steel foundation columns, coke, basic slag. 
1967 Became part of British Steel.