A little more detail regarding the jewels in our ETA/clone movements.
17 jewels was all that were required for these and most simple movements until the jewel wars heated up. ETA added the extra jewels into the winding module where most of them went into the two reversing gears. Most experts at the time found this to be a marketing ploy more than an actual benefit since, one, they were not in use near as much as in other parts of the gear train that were jeweled and in constant motion, and secondly, those parts were very cheap and easy to replace during a normal servicing. So in reality the older 17 jewel movements are just as reliable.