I found this page that Bet You Don't Know How Old Sequential Turn Signals Worked.  It is not that complicated

That link just gives me a blank page 

Try this one : https://www.youtube.com/watch?v=P_4yYp5tqEg&t=18s The older mechanical sequential systems are cool ! I have them in my 1966 Thunderbirds. Usually , all it takes to get them working right is to just file the contacts a bit to get a good connection .

That's better, I like that guy's username   

That's about how I figured the old mechanical ones worked. Similar devices were used to create the chasing lights on signs. A more complicated controller also using cams and switches were used to switch traffic signals.

Not seen one like that before.

I know they used to use a slow-rotating motor driving a shaft with cams and microswitches on to drive the flashing displays on fruit machines back in the day, those were interesting.

I believe some school buses still use some for the 8-way flashers. You can tell they use them because when they switch on the amber lights, sometimes one will flash very briefly before the other one lights if they were stopped mid-flash the last time.

I have a motor driven school bus flasher somewhere !