Perry,

The Bulle and the Allion brands are one-day clocks.

You never know what you might find at the National Air and Space Museum in Washington D.C.

Some information about at least one application of the Allion aircraft clock:

This Allion aircraft clock was part of the instrumentation of a Voisin VIII bomber. The clock shown in addition to other luminous instruments were used for navigation during night bombing raids.

Several years ago when I saw that Allion a Versailles clock from the Voison VIII night bomber at the National Air and Space Museum I was able to talk to the curator of the museum. He said that since this aircraft is hung from the ceiling people were not able to see into the cockpit they removed the clock and altimeter and placed them in that lucite case which is on the wall under the bomber. He also told me that the clock was originally bolted to center hub of the main control wheel which is like a big wooden steering wheel kind of like what you see on very old cars that is on a stalk that comes up from the floor through pilots legs. The pilot used this wheel to control the aircraft - turning it like a car steering wheel left and right to make the plane bank left and right, and pushing and pulling on it to push and pull the stalk forward and back to make the plane's nose go up and down. I thought it was interesting that this clock was not mounted on the control panel like other instruments typically are.

I had some free time last night to take some photos of my WW I French aircraft clock collection. The French, like the Americans mainly used clocks in their aircraft rather than pocket watches mounted in dashboard holders which is what the British, Germans, and Austrians mainly used used during the Great War. Eventually, in the years after the war all air services went to using the French and American approach and went to clocks.

Information on WW I French aircraft clocks seems to be almost non-existant - at least so far as I have been able to find. The only style of the below pictured clocks that I have actually seen in a WW I French aircraft is the Allion a Versailes in the shock mounted case, but the other three styles of clocks I show below - the Allion a Versailles in the regular case, the Favre Bulle, and the no-name Aviation Militaire are all of the same style and patina, and I have always seen them mentioned as being from WW I French aircraft. If anyone knows for sure whether these other three styles are definitely WW I by having seen them in either actual aircraft or in cockpit photos of the era or in some reference book I have not yet found I would very much like to hear about them. Also, if anyone has any additional types of WW I French aircraft clocks I would very much like to see them or hear about them. So far as I know there are only these four types. (The types that Enzo shows earlier in this thread are all WW II and just before WW II rather than WW I)

This first photo is of the five WW I French clocks in my little collection - the two on the top row are of the same model - both are Allion a Versailles in the shockproof case. The bottom left is the no-name Aviation Militaire style, the bottom center is the Favre Bulle style, and the bottom right is the Allion a Versailles in the regular case style.

Here are three photos of the no-name Aviation Militaire type. Many of the examples I have seen of this type have had the marking "Aviation Militaire" scratched off - you can see where it was by the scratches there on the dials. I am not sure why this is the case, but my only guess is those were surplussed after the war some time and were defaced to show they were no longer property of the French air service. My example has the markings intact and very readable:

These three photos of one of my two examples of the Allion a Versailles in the shockproof case type:

These three photos are of my example of the Allion a Versailles in the regular case type. The cathedral skeleton hands are correct but they have been relumed at some point which is why they look kind of white:

These three photos of my example of my example of the Favre Bulle type. This is the only type that was made without radium markings - it was non-luminous:

And finally, here are some photos of an old French air service blueprint I came across at the Air and Space Museum library. It is undated, but the design is for the Allion a Versailles in the regular case. The layout of the dial also fits the other types of clocks. My guess is that this was developed for procurements during WW I and that there were likely similar blueprints with the same standard dimensions for the other suppliers. I have no proof of this though - this is just a guess at this time. The first photo is of the overall blueprint and the photos following it are closeups of various areas: