Unlike the majority of the old constitutions, which are written on rolls, the Cooke manuscript is written on sheets of vellum, four and three-eighth inches high and three and three eighth inches broad (112mm x 86mm) bound into a book, still retaining its original oak covers. The manuscript was published by R. Spencer, London, in 1861 when it was edited by Mr. Matthew Cooke — hence the name. In the British Museum's catalogue it is listed as "Additional M.S. 23,198", and is now dated to 1450 or thereabouts, although errors in Cooke's transcription caused it originally to be dated to after 1482. In line 140, "And in policronico a cronycle p'yned", Cooke translated the last word as "printed", causing Hughan to give the earliest date as Caxton's Polychronicon of 1482. Later retranslation as "proved" justified the earlier dating. Obvious scribal errors indicate that the document is a copy, and repetition of part of the stories of Euclid and Athelstan seems to indicate two sources. Speth postulated, in 1890, that these sources were much older than the manuscript, a view that remained unchallenged for over a century.