S-21 was a high speed German motor torpedo boat, at a length of 33mtrs and powered by 3 Daimler Benz marine diesel engines, she was capable of speeds up to 44 knots. Her armament consisted of 2 x 21 inch torpedo tubes with 4 torpedoes carried, 3 x 20mm cannons, 1 x twin and 1 x single along with a single 37mm flak cannon. The S in S boat stands for schnell, this meaning fast in German, the name given to these craft was Schnellboot (Fast boat). 

Cowpen Drydock & Shipbuilding Co, Blyth, builders of the Corbrook. On the 2nd March 1883 the Blyth Shipbuilding & Dry Docks Co was registered as a limited liability company. The company built liners, tramp steamers and colliers. In 1914 a cargo ship that was under construction was purchased by the admiralty and converted into a aircraft carrier, namely the Ark Royal. During WW1 the company built various naval vessels for the Admiralty. After the war the company returned to the construction of civilian merchant vessels. Due to the post war slump and collapse of the freight market the yard shut.

In November 1926 Robert Stanley Dalgleish, a Newcastle ship owner purchased Blyth Shipbuilding & Dry Dock Co. The yards name was changed to the Cowpen Dry Dock & Shipbuilding Co and was later almalgamated with Ritson's Shipbuilding & Engineering Co. After completing a number of vessels, the yard closed in 1930. 

1937 saw the yard reopen under its former name. During WW11 the company was for the most part engaged in the building of British Naval vessels. In 1967, due to the company having run at a loss for five years, the yard closed its doors for the last time.

George Clark Ltd, builders of the Corbrook's engine. George Clark(e), Southwick Engine Works, Crown Road, Southwick, Sunderland

1848 George Clark founded his business at Monkwearmouth.

Mainly engaged in manufacturing pumping and winding engines for collieries and ironworks and marine engines.

1864 The founder's son, George Clark (1843-1901), took over the direction of the company from his father due to his illness

Increasing business led to the company moving premises twice - the second move was to the Southwick Engine Works which were erected in 1872

1885 January 15th. George Clark senior died.

1914 Directory: Listed as Mechanical Engineers 

1938 Private company - became part of Richardsons, Westgarth and Co

1961 Marine engineers, manufacturing "Clark-Sulzer" diesel engines. 1,300 employees. 

Later George Clark and N. E. M. Ltd (Credit Graces Guide)

Corry Colliers Ltd (house flag), owners of the Corbrook at the time of her loss. Cory Colliers Ltd (W. M. Cory & Sons) London, owners of the Cordene. The house flag of Cory Colliers Ltd, London. A red, rectangular flag with a white diamond in the centre. Cory Colliers were a branch of William Cory and Son. Originally in the coal trade, they became tug operators, taking over several other companies. In 1985 they were consolidated under the control of Cory Towage Limited, and the flag emblem was altered from a white diamond to a blue one edged white. They were taken over and absorbed by Bureau Wijsmuller in February 2000.