Can I wear the Master Ultra Thin daily?

Yes, with caveats. The 50m water resistance handles handwashing, rain, and light splashes. The thin case is more vulnerable to impacts than a sportier watch, so avoid wearing it during physical activities. For desk work, meetings, and social events, it's perfect as a daily watch.

What's the difference between Calibre 925 and 925AA?

The 925AA is an updated version with an extended 70-hour power reserve (up from 38-43 hours on the original 925). The movement dimensions are identical. The AA also benefits from improved accuracy testing under the 1000 Hours Control program. On the pre-owned market, the 925AA commands a $1,000-$1,500 premium.

Is the Master Control Calendar better than the Master Ultra Thin Moon?

They're different propositions. The Ultra Thin Moon is a dress watch: slimmer, more elegant, focused on aesthetics. The Master Control Calendar is a daily tool: slightly thicker but with day, date, month, and moonphase in one package. For a one-watch collection, the Calendar is more practical. For a multi-watch collection where you have a sports piece, the Ultra Thin Moon is the superior dress companion.

What is the thinnest Jaeger-LeCoultre watch?

The Master Ultra Thin Squelette measures just 3.6mm in total thickness, powered by the skeletonized Calibre 849SQ at 1.85mm. The Master Ultra Thin Jubilee (2013) was 4.05mm and held the world's thinnest mechanical watch record at launch. The hand-wound Calibre 849 at 1.85mm remains one of the world's thinnest traditional movements.

Is the JLC Master Ultra Thin Moon worth the money?

Absolutely. At $11,900 retail (or $8,500-$10,000 pre-owned), you get an in-house automatic movement with 70-hour power reserve, one of the most beautiful moonphase complications in watchmaking, 39mm sizing that works on any wrist, and JLC's 1000 Hours Control certification. It's widely considered the best moonphase dress watch under $15,000.

JLC Master Control Calendar vs. Longines Master Collection Calendar?

Both offer complete calendars with moonphase. The Longines is remarkable value at ~$3,000, but uses a modified ETA movement. The JLC uses fully in-house Calibre 866AA with 70-hour power reserve, superior finishing, and the unique jumping date mechanism. The JLC is genuinely a different class of watchmaking. If budget allows, the JLC is the clear choice.

How often does the moonphase on a JLC need adjusting?

The moonphase display on the Master Ultra Thin Moon (Cal. 925/925AA) is accurate to one day every 122 years. In practical terms, you'll never need to adjust it in your lifetime: assuming the watch runs continuously or is stored on a winder.

Jaeger-LeCoultre Master Ultra Thin & Master Control Calendar: The Definitive Guide

Jaeger-LeCoultre holds the record for the thinnest mechanical movement ever produced: the Cal. 101, at 1.85mm, created in 1929. The Master Ultra Thin collection extends that legacy with contemporary dress watches housing in-house automatic and manual-wind calibres at case thicknesses from 7.45mm to 9.9mm. The Master Ultra Thin Moon (Ref. Q1368420, 39mm, Cal. 925/1, steel) retails at approximately $9,700 and is widely considered the single best moon phase watch under $10,000. Pre-owned examples trade from $6,500-$8,500. The collection also includes the Master Ultra Thin Date, the Master Control Calendar, and the record-setting Master Ultra Thin Minute Repeater Flying Tourbillon at 7.9mm. JLC holds over 400 patents and has produced over 1,300 calibres since 1833, making it the most prolific movement manufacturer in Swiss watchmaking. The Master Ultra Thin delivers that depth of manufacturing expertise in a refined dress format that competes with watches costing two to three times more.

We can source this

3 references we can source through our network.

Master Ultra Thin · Source It Master Ultra Thin · Source It Master · Source It

Specifications

MovementCalibre 866/866AA (automatic, 70-hour power reserve)

Frequency28,800 vph (4 Hz)

Water Resistance50m (5 bar)

Certification1000 Hours Master Control

History

JLC's ultra-thin legacy begins in 1907 with Calibre 145, a pocket watch movement of exceptional slenderness. The modern lineage starts in 1975 with Calibre 839, leading to the 1994 debut of Calibre 849 at 1.85mm, the world's thinnest traditional hand-wound movement. The Master Ultra Thin collection launched in 1993, and the Master Control Calendar was introduced in 2020 as the complete-calendar complement.

Iconic References

Buying Guide

• Dress watch purists seeking the thinnest possible mechanical watch
• Black-tie collectors who need a watch that vanishes under a French cuff
• Moonphase enthusiasts: the Ultra Thin Moon's disc is one of the most beautiful in horology
• Complete calendar fans: the Master Control Calendar is the best value in its category
• Watch people who want horological depth without flashy branding
• Professionals in law, finance, and consulting, these watches say 'I know watches' without saying a word

Pricing & Market Data

Retail MSRP

valueMaster Ultra Thin Date: ~$8,500 | Master Ultra Thin Moon (steel): ~$11,900 | Master Ultra Thin Moon (pink gold): ~$19,500 | Master Ultra Thin Perpetual (steel): ~$29,000 | Master Control Calendar: ~$10,500-$15,300

Pre-Owned Market

valuePre-owned Ultra Thin Moon: $8,500-$11,000 | Pre-owned Ultra Thin Date: $6,500-$8,800 | Pre-owned Master Control Calendar: $9,000-$14,000

Market Trajectory

Steady appreciation across the line. The Master Control Calendar launched in 2020 and has already built a strong following: prices are firming. The Ultra Thin Moon is stabilizing at a higher floor with the 925AA movement upgrade.

Investment Grade

B+ (Ultra Thin Moon) / A- (Master Control Calendar: exceptional value for the complication set)

Best Value Pick

Master Control Calendar Q4148420: complete calendar with moonphase, 70-hour power reserve, 40mm steel case, 1000 Hours tested, at $10,500-$11,500 retail. This is genuinely the best complete calendar watch under $15,000 from any brand.

Comparisons

Cultural Significance

Collector's Lore

The Calibre 849 story is the stuff of legend in the Vallée de Joux. At 1.85mm, the movement is so thin that a single fingerprint during assembly can cause issues: JLC watchmakers wear special cotton gloves and work under nitrogen-controlled environments when handling the 849's mainspring. The barrel is 'hanging' (suspended from above rather than seated in a plate)to save 0.2mm of height. When JLC released the Ultra Thin Jubilee at 4.05mm in 2013, they also created a matching fountain pen case that was thinner than the watch. Collectors who attended the launch event in the Vallée de Joux received the watch in a custom-milled aluminum case only 15mm tall. The Master Control Calendar has a secret Easter egg: the jumping date hand that leaps across the moonphase was designed by a JLC engineer who was frustrated that every other calendar watch's date hand obscured the moonphase twice a month. His solution (make the hand jump)is now patented.

Frequently Asked Questions

Related Guides

Direct Comparison

Piaget Piaget Altiplano: Ultra-Thin Guide, References, Calibers and Pricing

The Piaget Altiplano is the ultra-thin dress watch that most other ultra-thin dress watches are measured against. Piaget...

Read guide →

Direct Comparison

Audemars Piguet Audemars Piguet Royal Oak Jumbo Extra-Thin

The Audemars Piguet Royal Oak Jumbo Extra-Thin is the founding document of the luxury sports watch category. Gerald Gent...

Read guide →

Direct Comparison

Omega De Ville Prestige

The De Ville Prestige is the dress watch we sell to the customer who wants Omega craftsmanship without the Speedmaster o...

Read guide →

Same Brand

Jaeger-LeCoultre Duomètre

The Duomètre is the watch that lets a Jaeger-LeCoultre run a chronograph, a foudroyante, a moon phase, or a tourbillon w...

Read guide →

Same Brand

Jaeger-LeCoultre Jaeger-LeCoultre Geophysic Buying Guide, Specs & Prices | Ultimate Watch

The Jaeger-LeCoultre Geophysic is one of the quieter greats in the JLC catalog, and that is exactly why collectors who k...

Read guide →

Same Brand

Jaeger-LeCoultre Jaeger-LeCoultre Grand Complications: The Watchmaker's Watchmaker at the Pinnacle of Horology

Jaeger-LeCoultre Grand Complications represent the full manufacturing depth of the Vallée de Joux's most prolific calibr...

Read guide →

Own a Jaeger-LeCoultre?

We buy Jaeger-LeCoultre watches at competitive prices. Fast payment, no obligation quote.

Get a quote →Browse Jaeger-LeCoultre inventory →