[8] Even Tollefsen was the son of Torleif (Tollef) Hansen (1806–1885) and Kristine Marie Evensdatter (1807–1860)[6] and was born at Østre Oterbekk on the island of Nøtterøy.

In 1897 he was captain of the full rig Magnhild when the coal cargo shifted during a storm off the coast of Newfoundland and the ship went down.

[8] Rebuilt sailing ships with oil in wooden tanks had their heyday in the 1880s, but throughout the 1890s they were out-competed by steam-powered iron tankers.

[8] Tollefsen did not patent his inventions and, although foreign shipping companies used his system for many decades into the 1900s, they failed to credit him, and so his name was quickly forgotten.

During the Jubilee Exhibition at Frogner in 1914, the shipowner Gustav Conrad Hansen was honored as the creator of the world's first tanker ship owner without Tollefsen's name being mentioned.

Henry Tschudi (1858–1939)[11] and Axel Camillo Eitzen, both of whom had followed Tollefsen's work at the Fagerheim shipyard and participated in the subsequent oil-freighting period, made the world aware that Tollefsen alone deserved the credit for the technical innovations, whereas the shipowner Gustav Hansen was a businessman that was able to financially exploit the invention.