Like many brands – there is a big confusion on references between different market when it comes to vintage Jaeger-LeCoultre.
So far, my conclusion is that there are three major reference systems in use pre-1970 Jaeger-LeCoultre.
The most well-known reference system is the Swiss, which is a number system with an “E” in front of the number if the watch is waterproof, the E stands for Étanche as in waterproof in French.
Then you have the French reference system which is based on numbers and letters, where the letters describes the watch.
For example, the French reference for the Geophysic is “12 R.E.SC.19” while Swiss system have it as E 168.
12 = Movement size, number of lines. R.E.SC = Round case, waterproof, central seconds. 19 = the unique number of the watch for the “12 R.E.SC.” combination.

The third which is quite unknown and much harder to trace is the U.S. reference system.
The U.S. reference system is also a number system – once I have gathered more data, I will give you my thoughts on how it is built – but for now I will give you an example of a watch which both have a Swiss and a U.S. reference: the Jaeger-LeCoultre reference 390 / the LeCoultre reference 2406.
Next up on the Wooden Beam, the LeCoultre 2406:

Lately I have been reporting on several “His and Hers” watches made for the U.S. market – the 390/2406 is another of these couples watches with the difference that is was not only made for the U.S. market.
Back in the early-mid 1950’s there were a lot of “His and Hers” watches but the 390/2406 is later – early 1960’s which is a bit surprising since in the 1960’s females were much more independent and one might think that couples would be less likely to engage a “watch pair” relation…
I have no year of release – I have found documents from 1961 – 1963 with the 390/2406, my watch is from 1961-1962 based on the movement number.
The asymmetric shape originates from couples watches of the 1950’s, shown below is the LeCoultre Aristocrat. Often referred to as the “Grasshopper” due to its shape.

Without the “Grasshopper” legs, the 390/2406 have a much more elegant and slender look. While the Aristocrat is kind of flat in profile with rounded corners, the 390/2406 is anything but flat and with sharper corners.

Here is the His and Hers shown in the 1963 European Jaeger-LeCoultre catalogue: notice that the cases are 18K solid gold while the 2406 in the U.S. were offered in 10K gold filled case and 14K solid gold.
I have noticed several versions of the 2406 case with pattern on the bezel or like mine – polished all around. Even some versions with diamonds on the dial…
The smaller ladies version, Swiss reference 1664, U.S. reference 2416.

As you may remember from my previous reports, in the U.S. market, names were often used instead of reference numbers – here in a Christmas LeCoultre ad from 1961 – Lady Anne in 14K gold:

I am still to figure out what name was used for the 2406…
In this shot it’s clear to see that all lines are in a slightly bent shape – both from top to bottom and from side to side.
Size: 28/23 mm wide and 27 mm high, 35 mm lug to lug and 19 mm between the lugs.

Even the case back have bevels which makes it very comfortable on the wrist…
Inside is the manual Calibre 438/4CW – same as in the LeCoultre Sultan.

In profile the dome crystal dominates, but if you look at the bezel/lugs you can see that bevels are quite big!

On the wrist, I find the 390/2406 very elegant, very comfortable!

Stay tuned for more watch reference reports!