Jaeger-LeCoultre Master Ultra Thin Perpetual Calendar: A 4-Year Ownership Review

Key Points from the Discussion

• The perpetual calendar module in the JLC Master Ultra Thin Perpetual Calendar shares design similarities with IWC's Kurt Klaus perpetual calendar, particularly in the layout of the moon phase, date, month, day, and four-digit year display. This suggests a common module or licensed technology, rather than an entirely reinvented complication.
• While the JLC Master Ultra Thin Perpetual Calendar utilizes a JLC base caliber, the perpetual calendar mechanism itself is widely understood to be a module, possibly from Dubois-Depraz, integrated into the movement. This is a common practice in watchmaking, where specialized complications are added to existing base movements.
• The IWC Kurt Klaus perpetual calendar is often based on an ETA movement and is generally larger and thicker. In contrast, the JLC Master Ultra Thin Perpetual Calendar uses a JLC base caliber (e.g., Caliber 868/1), making it a distinct, thinner execution despite potential module similarities.
• For perpetual calendars, a watch winder is highly recommended due to the complexity of setting the calendar if the watch stops. While manual adjustment is possible, going backward is not easily done, making a winder a practical accessory for owners.
• The 39mm case size of the JLC Master Ultra Thin Perpetual Calendar offers excellent wearability due to its thin and light profile (66 grams with strap and buckle). However, some users, particularly those with evolving eyesight, might find the day display challenging to read without corrective lenses.
• The visual similarities between the JLC and IWC perpetual calendars, particularly the dial layout and four-digit year indicator, raise questions about shared design language or components within the Richemont group, even if the underlying movements differ.