I have seen a picture of one of these on a driveable Franklin. I recently acquired just the cowl from a 1928 Franklin and now I have an actual unit. I still don't know what it is. Get in on the fun and add your guesses to mine.
PS; The picture needs to be rotated 90% to the left to show it's actual position. One end of it is mounted to the vertical surface of the cowl above the terminal strip on the drivers side.