Graduated bar scale, with measurements corresponding to 1:48. Drawing titled 'A Design for building Iron Frigates of 36 Guns & 1250 H.P. [horsepower] having 214 feet of their length covered with Armour Plates of 4 1/2 inches in thickness on the outside, named "Warrior" & "Black Prince"'. The title has been amended by the following note in red ink: 'as of 28 September 1860 to have 40 guns'.

The plan shows the body, sheer lines and longitudinal half-breadth of the Warrior class broadside ironclads Black Prince (1861) and Warrior (1860). The original lines have been altered at the bow in red ink to illustrate changes in the original design relating to Black Prince and the broadside ironclad Achilles (1863). A cover note in red ink at the bottom right hand side of the plan reads: 'The lines in red are in accordance with the Drawing sent to Mr. Napier at Glasgow [where Black Prince was built] on the...October 1859 for building the Black Prince [no date given, but Black Prince's keel was laid on 12 October that year]. The red dotted lines represent the Achilles'.

There are seven signatures on the plan belonging to the following:
Rear Admiral Sir Baldwin Wake Walker [Surveyor of the Navy in 1859]
Isaac Watts [1st Assistant Surveyor in 1859]
Joseph Large [2nd Assistant Surveyor in 1859]
James Graff [Draftsman 1st class in 1859]
William G. Romaine [Second Secretary to the Admiralty and a Commissioner of the Admiralty in 1859]
The Right Honourable Sir John Somerset Pakington [a Commissioner of the Admiralty in 1859]
Vice Admiral William Fanshaw Martin [a Commissioner of the Admiralty in 1859]

The plan was drafted by James Graff at the Admiralty, Whitehall.