Royce's greatest early triumph, which marked the establishment of a car of real quality and the one which brought significant international recognition to the firm, was the introduction in late 1906 or early 1907 of a six-cylinder chassis wherein an L-head engine was built as a combination of two three-cylinder blocks bolted to an aluminum crankcase. This famous engine initially had "square" dimensions with bore and stroke of 114.5mm or 4 1/2 inches. The stroke was later increased to 4 3/4 inches, yielding 7428cc displacement. This 429 cubic inch engine received the RAC (taxable) rating of 48.6 HP based on a formula independent of RPM and true power output. The engine has a beautifully machined crankshaft running in seven main bearings, the center one between the blocks being of increased size. The four-speed gearbox and final drive provided ratios of 2.7, 4.2, 5.9 & 8.5 to 1. A then-unconventional flexible radiator mounting, A Royce-designed carburetter and electrical fittings, and beautiful construction and machining are notable in this car. The side-by-side valves in the engine are operated by a single camshaft through rocking levers and anti-friction rollers; oil lubrication is provided through a full-pressure system by a gear-wheel pump, and from 1908 onward an extra oil valve was opened when the throttle reached its three-quarter point to force oil directly to the cylinder walls, thus offering high-speed protection against wear. At the beginning the car was simply known as the "40.50 HP Model", but the thirteenth chassis made was fitted out with a silver-painted, four passenger touring body with silver-plated fittings. A small plaque on the scuttle below the windscreen bore the legend "The Silver Ghost". Although this is the name for that individual car and it is indeed the original Silver Ghost, the name soon became applied to all these 40/50 HP, six cylinder cars with the L-head engine.