They have a common chassis, except that the cylinders, 20 in. diameter in the Class "7", are linered down to 19½ in. in the Class "6".1951 July, “British Standard Locomotives”, in Railway Magazine, page 444:
LINER
noun
1
Initialism low ionization nuclear emission line region
A good liner has a pretty shrewd idea of the value of the painting he is treating and usually charges accordingly.1973, Kyril Bonfiglioli, Don't Point That Thing at Me, Penguin, published 2001, page 41:
2
A removable cover or lining.
I threw out the trash can liner.
Lane Coutell, in a Burberry raincoat that apparently had a wool liner buttoned into it, was one of the six or seven boys out on the open platform.1955, J. D. Salinger, “Franny”, in Franny and Zooey, Boston, Mass.: Little, Brown and Company, published 1991, →ISBN, page 3:
3
The pamphlet supplied in the box with an audiovisual tape or disc, etc.
liner notes
4
A lining within the cylinder of a steam engine, in which the piston works and between which and the outer shell of the cylinder a space is left to form a steam jacket.
5
A similar lining for cylinders of internal-combustion engines (see "Further reading").
6
A slab on which small pieces of marble, tile, etc., are fastened for grinding.
A large passenger-carrying ship, especially one on a regular route; an ocean liner.
With her luxurious furnishings and spacious accommodation the Invicta, which is 350-ft. long and has a gross tonnage of 4,178, resembles a small liner.1947 January and February, “Notes and News: New Southern Channel Steamer”, in Railway Magazine, page 49:
He turned back to the scene before him and the enormous new block of council dwellings. The design was some way after Corbusier but the block was built up on plinths and resembled an Atlantic liner swimming diagonally across the site.1963, Margery Allingham, “Foreword: The Turk Street Mile”, in The China Governess: A Mystery, London: Chatto & Windus, →OCLC, page 9: