A contract between the Conservators of the River Thames and Messrs Fleming & Ferguson Limited for the construction of four steam hoppers, dated 23rd July 1906. Also included are the conditions of tender and a specification containing general requirements along with details of the hull, machinery and furnishings to be supplied. There is a handwritten note on the front stating that these hoppers would be Thames Conservancy, later Port of London Authority, hoppers numbers 5, 6, 7 and 8 and that during the First World War they would be converted to fleet oilers and named Blackol, Greenol, Purfol and Silverol.