The first free winding rotor

The need

Harwood’s weight banged between buffer springs through half a turn. Rolex also needed a way to wind the sealed Oyster without unscrewing its crown every day.

Made by

Rolex with its movement maker Aegler of Bienne, in work credited to Emile Borer.

What was new

A half-moon weight pivoting at the centre of the movement and turning through a full 360 degrees, quietly and without buffers. A slipping clutch stops the mainspring being over-wound.

Worth knowing

Fitted in the sealed Oyster case, it became the Oyster Perpetual. When Rolex’s patent expired at the end of the 1940s the rotor became the industry standard. It wound in one direction only; winding in both came about twenty years later.

Historian’s noteRolex did not invent the self-winding wristwatch; Harwood did. 1931 is the year of the invention and patent work, with watches reaching customers in 1932 and 1933.

SourcesRolex