Looks like an accessory add on switch to me for anything from a spot light to basic heater fan motor. But most likely some type of lamp.
If you say you've seen it before on another car in the same place it is possible it is a factory crude add on for say a dashboard lamp on some cars of the same run.
Though most external mounted dash lamps had their own toggle or push and turn body ,many did use a remote switch .Naturally dash gauges lit from behind had to have a switch some place.
My 23 Star gauges(Oil and Amp-meter) are designed to be lit from behind but there Is no lamps provided as they are not in a cluster format. I would have to install and external lamp and may have to use such a switch to do it..
DMS
Where Are You From? Ct
Do You own a car built by Durant? '23 Star Touring
Looking at the wiring diagram of the 1925 Star 4 cylinder it shows a seperate switch for the dome light and "could" be located in the dash, most other models show them to be at the dome light itself.
I thought this was to turn on and off the dash lights. I know some of our cars have the switch for this. A lot of our era cars had a separate switch to turn these on rather than they come on automatically when you turn the headlights on. Don't known why but manufacturers did this.
Where Are You From? Oviedo, Florida
Do You own a car built by Durant? 1928 Durant Model 65
AH! I see in your picture you have the standard Model A Ford amp-meter ,with out question. But I won't tell , oops.:) I'm trying to jam one behind / into the original '23 Star bezel so it can replace the external mounted(Dodge?) and make a cleaner dash front by mounting behind the dash again .
Don't worry about that silly innocuous switch. It's for the original "ejection seat" incase you ever hit the sound barrier and need to bail before the car falls apart from vibration.
DMS
Where Are You From? Ct
Do You own a car built by Durant? '23 Star Touring
Ah the ever wondering what switches were for, all part of Durant's no two cars the same on same model ..
Have my own with the 32 and what was it for. Hole to left of lighter where key should be. In its past some owner switched lighter and ignition. Perhaps a lefty with lighter and ash tray to left of column. Wondered what the hole was for. I've seen a push button on one or two Durant's and De Vaux dashes, in same place. Most don't have it.
Here it is again on a 1930 614 parts car.
Where Are You From? Ottawa Ont
Do You own a car built by Durant? Dominion built 1932 614 Sedan
The picture that I posted above was one I found off the internet (http://www.autonetlocator.com/view-1926-durant-star-photo-details-msgf.html). My dash looks like this:
I was thinking that all of the extra switches had been added after the car was built, but when I found the picture of another car with what lookers like the exact same switch, I started thinking it might be "original" equipment. Does anyone know if the Coupes had an overhead light? Mine does not, but if they did it seems likely that that is what the switch goes to.