Mystery part

I recall reading that Kaiser Wilhelm II had one of these in his limousine.

This is a version of the passenger half of a “William’s Electrical Signalling Device for Motor Cars and for other Purposes, available for Night and Day Use”. Patent 7828/1905 was awarded to William Edwin Williams of 47 Croftdown Road, Highgate, London and it claims:

“May also be used in ships, factories and other buildings, and for a great variety of purposes. When used in a motor car it enables persons seated in the passenger compartment to give instructions to the driver. It consists in an electric arrangement which rings a bell and then lights a lamp behind a transparency, placed so as to be easily seen by the driver, on which are written orders or messages such as: “slower” “faster”, “stop”, “home”, “left”, “right”, “ahead”, “astern”, and the like. The mode of operating the device is to depress the button or switch which is identified with the message to be given”.

Evidently, it was in use as early as September 1902, when “The Car” described “a capital arrangement by which the Duke of Marlborough is able to signal to his chauffeur without admitting to the interior of the car any samples of our estimable climate. This in an indicator which is fixed on the dashboard. The dial bears the words "Stop," “Go on," "Turn to the left," " Turn to the right," " Go slower," "Go faster,” ” Turn right round." A slight pressure upon an electric button is all that is necessary to indicate any one of these instructions.”

Napier Cars later likened it to a ship’s engine-room telegraph and by 1906, their coachbuilders and other’s fitted similar units, plus a speaking tube and dual speedometers for passengers and driver, into Pullman type limousines.

Ik heb nog een paar vragen aan de eigenaar.
1. Zijn de onderste twee knoppen verend, dwz springen zij terug of blijven ze ingedrukt?
2. Als dat laatste het geval is, kan men dan met de ene knop de andere laten terugspringen?
3. Dezelfde vraag met over de knoppen op het apparaat: veren die terug of blijven ze ingedrukt?
4. Indien het laatste het geval is, kan men dan met de linkerknop onderaan Faster, Left, of Stop doen terugspringen?
Tenslotte: is er bij het indrukken van een de knoppen een mechanisch geluid te horen.

Hierop kan ik alleen in het nederlands reageren. In eerste instantie denk je aan een vestzakhorloge gezien de ronde lus bovenaan. Maar dat kan ook dienen om het apparaat op te hangen. Onderaan is een halfrond gat. Als we er van uit gaan dat vandaar een kabel liep vandaar naar de chauffeur, dan blijft er nog een groot raadsel: waarvoor dienden die twee ronde knoppen onder aan ?

Does it predate the horseless carriage?

I feel it must be an electrical machine the size of an alarm-clock hung in the owner's part of a coupé chauffeur with which, on pressing the adequate knob, the same light lights in front of the chauffeur and he can follow his master's orders.
If the owner wants go to back home, he presses the HOME knob and the chauffeur knows it without talking.
It probably worked much better than the older acoustic system.
I could have said it better in French!
Jean

No real mystery - it is the control for a a limousine of chauffeur drivers lamp - on the dash would be a round bezel with lights around it to light up corresponding to this switch.