Here's a breakdown of the situation:
* Purpose of Jewels: Jewels (typically synthetic rubies or sapphires) are used as bearings to reduce friction in the movement's gears and other moving parts. Lower friction leads to improved accuracy, longevity, and reduced wear on the metal components.
* "Jewel Inflation": In the past, some manufacturers added non-functional jewels to increase the perceived value of the watch. These jewels weren't placed at key friction points and didn't improve performance. This practice led to consumer skepticism about high jewel counts.
* Practical Limits: A well-designed mechanical watch movement will have jewels at all critical bearing points. After a certain point, adding more jewels offers diminishing returns or no benefit at all.
* Typical Range: Most high-quality mechanical watches have between 17 and 30 jewels. The precise number depends on the complexity of the movement and the number of complications (e.g., chronograph, date, moon phase).
* Extremely High Jewel Counts: There are examples of watches with very high jewel counts (over 100, even exceeding 1000 in some rare cases). These are typically either:
* Novelty items where the number of jewels is a selling point, but not necessarily functional.
* Highly complex watches with many complications, where each complication requires additional jewels.
In summary: While theoretically there isn't a defined maximum, focusing solely on the jewel count is misleading. A watch with a moderate number of *well-placed* jewels in a thoughtfully designed movement is generally superior to a watch with a very high number of jewels, many of which serve no practical purpose. It's more important to consider the watch's overall design, quality of materials, and craftsmanship than the jewel count alone.