Chaluret 93 (2nd style) derailleur

At first look the Charulet 93 appears to be a copy of a mid 1930s Simplex Champion du Monde but with the addition of a surreal, sci-fi, pulley cage. But it is actually even more entertaining than this.

Like the Simplex Champion du Monde it is a single pulley, low-normal device operated by pulling a toggle chain. But with the Charulet 93 the pulley is offset from the p-pivot, and, as the pulley cage is pulled outwards towards the main arm, a peg running in a spiral groove causes the pulley cage to rotate clockwise. This rotation has three effects:

The first seems odd to me. This is that the pulley itself moves further from the sprockets - kind-of increasing the chain gap.
The second effect is that the, extravagantly curved, inner plate of the pulley cage moves closer to the sprockets - reducing the effective chain gap for the activation of the up change.
The third effect is that the outer plate of the pulley cage also rotates. This plate is very deliberately shaped to do something to do with the effective chain gap for the down shift - but I can't quite work out what.

Whatever is going on, this model rates highly amongst the most interesting derailleurs of 1930s - and that's a crowded and competitive field.

I have seen a number of suggestions about the date of introduction of this derailleur. For example Frank Berto in The Dancing Chain, gives a date of 1946. This probably comes from the date on which it appeared in a Daniel Rebour drawing from one or other cycle show. In contrast, I consider that it dates from 1939. My thinking goes as follows:

In 1938 Chalumeau et Menneret advertised a derailleur called the Huret Course Pro 83. Note that '83' is the reverse of the '38' from 1938. Chalumeau et Menneret probably manufactured the Course Pro 38 for Huret.
Sometime very shortly after 1938 Huret made moves to manufacture its own derailleurs.
In response Chalumeau et Menneret decided to manufacture their own model, and adopted a design created by Raymond Bon. This was the Chaluret 93.
As with the Huret Course Pro 38, I think that the '93' in Charulet 93 is the reverse of the '39' in 1939.
This strange habit of reversing the digits of the year was a bit of a fashion in the mid 20th century. A product named '39' is already out of date in 1940, but a product named '93' may not be. Just the other day (I write in 2022) I spent what felt like two lifetimes failing to overtake a sluggish and smoke belching truck on a narrow, twisty, country road. I was not overly impressed by the sticker on the back proclaiming that this particular model was 'truck of the year 2009'. Clear dates are dangerous things in the time-obsessed world of branding.
I have an advert for the Charulet 93 dating from 1944, which indicates that its launch date was before 1946.
I appreciate that the Second World War makes the idea of launch dates slightly cloudy. It is perfectly possible that there were no major bicycle shows between the release of the Chaluret 93 in 1939 and the 1946 season. A 1946 bicycle show may well have been the first opportunity for Chaluret to show their wacky derailleur to the likes of Daniel Rebour.

This example appears to be unused. It sports a generic, speckled, industrial paint finish. This appears to be a similar finish to that on the example featured in the May 1981 edition of New Cycling magazine.