Scale: Unknown. A model of the plan for repairing the boiler tube invented by Mr E. Clark in 1863. The model is made entirely in metal, in four separate parts. The first part is a central cylindrical section with a square base which has a paper label applied to its underside marked '11'. The second section is a slightly wider cylinder consisting of three overlapping metal plates that have been formed into a cylinder and this fits over the first section. The third section is a large cylindrical ring with a wide base that fits over the first two sections. The fourth section is a cylindrical ring with a wide top on which is cast 'E. Clark Pat 1863.' The fourth section fits between the first two sections.