The Mercier Valor was a design patented and manufactured by Novitas Fabrik Elektrischer Apparate A.G. of Zürich, Switzerland in 1932. Its Swiss origins are not so strange - Mercier was based in St Étienne, which is as close to Zurich as it is to Paris.

It is a simple, robust, touring (rather than racing) design. The cable pull rotates a drum with a spiral surface cut into its inside surface. This spiral acts on a bolt head screwed into the main rod that holds the pulley cage, moving it in and out as the drum rotates. All this is very reminiscent of the contemporary Cyclo designs. However, unlike the double cable, unsprung Cyclo, Mercier opted for a single cable with a spring in the derailleur. This spring pulls the guide pulley outwards - making the derailleur top normal. The derailleur also has rather well shielded moving parts - meaning that the grease was likely to stay in, and the mud was likely to stay out.

I believe that the Mercier Valor went through a number of development stages:

• The initial generation (1934?) had an external pulley cage spring that led from the tension pulley bolt to a fixing on the rear dropout. Initially the pulley cage arm was short (55mm centre to centre) and the tension pulley had large (60mm) flanges. I believe that these versions were initially branded 'Valor', but that this was soon changed to 'Mercier'.
• A second generation (1937?) was largely identical - but had a longer (70mm) pulley cage arm.
• A third generation (1938?) moved the pulley cage spring so that it led from an eyelet at the top of the pulley cage arm, along the chainstay to a clip. The tension pulley was also reduced in size to 50mm diameter. Finally this generation was available with either a steel or an aluminium pulley cage arm.

These dates are a touch spurious. The 1932 date of the founding patent is not in doubt. The 1934 date for the appearance of the first production derailleurs comes from The Dancing Chain. I have some adverts from 1936 also showing this first generation. And at that point my hard data really stops. If you have any 1930s Mercier catalogues which have real detail, I would be very interested!

I think this is a, well used, example of an early Mercier Valor from the first generation described above. I think it is a slightly later version than my Mercier Valor (1st style) because it is branded 'Mercier' and has a, fairly crude, rectangular-ish hole for the cable nipple. Some key features are:

• The pulley cage spring attaches to the tension pulley bolt.
• The pulley cage arm is steel and 55mm centre to centre.
• The tension pulley flanges are 60mm in diameter.
• The tension pulley is labelled 'MERCIER BREVETÉ S.G.D.G.'.
• It has a brass ferrule at the point that the cable passes thrtough the mounting plate.
• The mounting hole for the cable nipple is somewhat rectangular.

The pulley cage spring on this example has gone AWOL, but you can still see the spring attachment plate screwed onto the tension pulley bolt.

I obtained this derailleur along with its matching lever. You can see photos of this lever if you click on the 'photos' tab and scroll down. It is a large 3-speed indexed lever in which the indexing peg is constrained by slots, causing the rider to 'over-shift' before the lever slips back to the correct position. This is smart, and somewhat similar to Shimano's SIS system. In contrast to modern systems, the cable nipple is at the derailleur, and the cable clamp is incorporated into the lever - well away from road crud. Finally there is a well machined cable tension adjuster at the lever - where it is easy for the rider to access. All good stuff.

The round part of this lever is large - about 45mm in diameter. I believe that when the derailleur was later redesigned, with smaller discs at the tension pulley, the lever was also redesigned to be smaller.

• Derailleur brands: Mercier manufactured by Novitas Fabrik Elektrischer Apparate A.G.
• Country: France, manufactured in Switzerland
• Date of introduction: 1935?
• Date of this example: unknown
• Model no.: unknown
• Weight: 383g including mounting bolts and pulley cage spring
• Maximum cog: unknown
• Total capacity: unknown
• Pulley centre to centre: 55mm
• Index compatibility: friction
• Chain width: 1/8”?
• Logic: top normal
• B pivot: none
• P pivot: sprung
• Materials: mainly steel with some brass small parts and an aluminium tension pulley