INDEX (REGULATOR)

A DEVICE FOR ADJUSTING A WATCH’S RATE BY INCREASING OR REDUCING THE EFFECTIVE LENGTH OF THE BALANCE SPRING. THE INDEX IS A STEEL LEVER, THE SHORTER END OF WHICH CARRIES THE CURB PINS WHICH EMBRACE THE SPRING, AND THE LONGER END OF WHICH PASSES OVER A SCALE MARKED IN FRENCH A AND R (AVANCE AND RETARD) OR IN ENGLISH F AND S (FAST AND SLOW). THE INDEX IS FRICTION-FITTED ON THE BALANCE’S ENDPIECE. THE WATCH IS REGULATED BY MOVING THE INDEX FORWARDS; THE RESULT OF THIS CAN BE GAUGED FROM THE GRADUATIONS ON THE BALANCE COCK.