Launched in 1972, the Royal Oak was the world's first luxury sports watch housed in an imposing stainless steel case that cost more than a gold model. Touted as having "a body of steel and a heart of gold" the stainless steel armour of the Royal Oak, with its eight-sided bezel and exposed screws, had an industrial edge to it, while the "heart" in the equation referred to Audemars Piguet's Calibre 2121, an ultra-thin 3.05mm automatic movement with a gold oscillating weight.