1851 Great Exhibition: Official Catalogue: Class V.: Eastwood and Frost
From Graces Guide
672. EASTWOOD and FROST, Morledge Iron Works, Derby — Manufacturers.
Rolled bar, forming when bent a segment of a wheel; bar, forming the centre of a wheel, viz., the boss, arms, and rim.
Wheel-centre, complete, for carriages; and for engines. The wheel is made of wrought-iron, from rolled bars, so as to give strength and lightness to the arms and rim, and so secure uniformity of weight throughout.