The collection comprises 12 volumes of design notes, sketches, charts, trial results and correspondence relating to mechanical and marine engineering work carried out by Charles Sells at Maudslay, Sons and Field between 1842 and 1883. The volumes are numbered and cover the following dates; 1: ?1842 to 1847; 2: April 1842 to 1849; 3: January 1849 to January 1851; 4: June 1853 to December 1855; 5: January 1856 to March 1859; 6: March 1859 to November 1861; 7: November 1861 to May 1865; 8: May 1865 to December 1867; 9: December 1867 to January 1871; 10: January 1871 to May 1875; 11: May 1875 to April 1878; 12: April 1878 to March 1883. A full contents list of the first four volumes is available in the Library and Archive Reading Room.

A thirteenth volume, covering June 1851 to June 1853 is shelved in the Maudslay collection (ref: MAUD 13).