Don't get too exited about the missing millions. According to the Bosch Book
of the Motor Car: (in summary)

In 1893 JB Freeman fitted a roller to the back of the car that could be
worked by a cord to show "left" or "right". Other people followed this with
mechanical arms that swung out. By 1905 the signals were pneumatically
controlled and self-cancelling to the design of F Berger. In 1908 AG
Barrachini had added internal illumination by electric light with
"provision" to raise the arms electrically. In 1918 the Naillik Motor Signal
company was selling translucent arms internally lit raised by electric
motors. And finally in 1923 G Deneef and M Boisson added the linear solenoid
version.

Grand dads patent would have almost certainly been challenged by the big
boys. Lucas isn't mentioned but then it is the Bosch book.

Malcolm