One of the more famous Jaeger-LeCoultre movements is the Calibre 101 Duoplan. Since 1929 – to this day, the worlds smallest mechanical movement!
Number of parts have varied through the history, from originally 74 to today’s version with 98 parts. Size: 4.80 x 14.00 x 3.40 mm.
Approximately 1 gram and if that was not light enough, there is a skeletonized version which weights only 0.4 gram!
Even with the fame of the Claibre 101, or maybe due to its fame – a lesser known fact is that the Duoplan movement is a whole family of movements!
The name comes from the construction of the movement which is made in T.W.O planes – with the balance wheel on the upper plane and the gear train on the lower plane (dial side).
The required area for the movement reduced significant without the need of reducing the size of balance wheel.
Here is a scan from an early 1930’s Italian Jaeger-LeCoultre catalogue:
(Google translation – unfortunately, my Italian is on the same level as my French)
The Duoplan revolutionizes watchmaking.
The precision and safety of its function allow us to offer it to the public with guarantees until now ignored in an industry as delicate as watchmaking.
Duoplan is characterized by:
- The movement built in two planes.
- The ultra-fast swing balance wheel.
- The stainless steel case.
- The unbreakable synthetic sapphire crystal.
- The waterproof winding crown located under the case.
- The international service of free and instant repairs.
- Insurance against loss, theft, and irreparable damage.
Point 1 – 5 are interesting points related to the watch construction – point 1 we already touched…
Point 2. ultra-fast swing balance wheel – this refers to the increase from the beating rate of 18000 vph/2.5 Hz to 21600 vph/3.0 Hz (remember that back in the 1930’s 18000 vph was the normal. Compared with the 1970 “Speed beat” which beat at the rate 28800 vph).
Point 3. stainless steel cases – not used by all brands at this point. Many brands used chromed brass alloy cases for their watches which was easier and cheaper to manufacture, but not as durable as stainless steel. All the way into the 1950’s man brands, including Jaeger-LeCoultre made a lower price range of watches with chromed brass alloy cases. This can be observed by a “B” beside the case number on Jaeger-LeCoultre watches.
Point 4. unbreakable synthetic sapphire crystal. Again, something which was not used by all brands or on all watches. Jaeger-LeCoultre used sapphire crystals on very few of their watch models, all the way into the 1970’s when mineral crystals started to become more common. To me, this indicates how very high Jaeger-LeCoultre regarded these Duoplans!
Point 5. waterproof winding crown located under the case – rather surprising, but yes, the crown was waterproof. I suspect that in today’s measurement, it would be considered water resistant, but not water proof. The second part here – crown located under the case, yes, all Duoplan movements have the crown on the back, but not all movements with the crown on the back are Duoplan movements!
This have caused some confusion among collectors, will try to clarify this – but first, let’s have a look at the Calibre 101, the Queen among the Duoplan movements!
4.80 x 14.00 x 3.40 mm – 1 gram! Invented in 1929, long before any computer aided design tools or simulations!
As you can see in the movement specification, the crown is located on the back, centric on the side opposite of the balance wheel.
Calibre 104 – Duoplan movement with the same layout as the Calibre 101 but larger: 5.80 x 16.00 x 3.40 mm – 1 mm wider and T.W.O mm taller than the Calibre 101, still a very small movement.
What is a bit odd when reading the movement specification for the Calibre 104, is the beating rate: 20222 vph. Never noticed any other movement with that rate. Could be a typo, but as it is very specific… Normal is a rate based on a multiple of 60.
Calibre 403 – Duoplan movement with the crown positioned in the top right corner, see blue arrow below. Still small, but significantly larger than the Calibre 101/103: 8.50 x 20,00 x 3.73 mm. The Calibre 403 came in T.W.O versions, 18000 vph and 21600 vph.
All Duoplan movements have the crown on the back, but not all movements with the crown on the back are Duoplan movements.
Calibre 406 – Baguette movement. This is a very similar movement from the outside as the Duoplan movements, but after consulting the Jaeger-LeCoultre Heritage Gallery I got confirmation that the Calibre 406 is indeed a baguette movement. Like a traditional movement, there is a main plate and bridges, but here the bridge looks very much like the Duoplan bridge due to the small size – but the mechanisms are in one plane as a traditional movement unlike the Duoplan.
As can be seen in the specification, the crown is located on the back, but centric on the long side. Another tell from the dial side is the beveled ends (Duoplan movements are flat) and the lack of additional mechanisms visible from the dial side (compared to traditional movements).
Calibre 409 – Duoplan movement is the largest in the family: 10.50 x 23.00 x 4.00 mm. The Calibre 409 existed with 18000 vph and 21600 vph versions.
One noticeable difference except for the size, between the Calibre 403 and the 409 is that they are mirrors of each other in layout, which results in them having the crown, still on the back but on opposite sides.
These Duoplan movements were combined with several different dial versions and case models which resulted in a large numbers of different references.
While studying documents I have come to the following interpretation – the Calibre 101 and 103 are rather rare and were often made in very small series. Not even sure if each model have a reference as such.
The Calibre 403 and 409 were more common and were made in larger series, still you see less of these than the Reverso from the same time period. Possible, less of the Duoplan survived as they didn’t have the protecting Reverso case..?
Each model had a specific reference, also all or most model existed with both movements, just different sizes.
The larger Calibre 409 references in the 600-series and the smaller Calibre 403 references in the 800-series.
For example, in previously I showed the reference 612/Calibre 409 in stainless steel and here is a scan with the reference 812/Calibre 403 in gold. Same model/case shape, just in different size/Calibre inside:
In the bottom of previous scan is the reference 803 in gold/white dial – here is my stainless steel version of the reference 803 with black dial:
Duoplan watches were offered to both ladies and gentlemen – in many different shapes and sizes:
Remember the reference 612 from the catalogue scan?
Here is my black dial version – it’s easy to see that the origin of the Reverso ONE Cordonnet was created at the same time as the reference 612:
One by one it is hard to see the size difference, but side-by-side it clearly shows – left, the 803/Calibre 403 – right, the 612/Calibre 409:
As mention earlier, the Calibre 403 and Calibre 409 are mirrors of each other, making the crown position in opposite corners:
The Calibre 409 was also used in the men’s versions of the Duoplan, but that is a report for another day…
Stay tuned for more!