Going through some watches I picked up I found this big boy and wondered what it was used for.

I´ll contribute with what little I know:
The innermost register is minutes measured time.
Next is the hour register.
The third (red) I don´t know.
The next black is minutes for the watch and doubles as seconds for the chronograph function.
The outer blue register is for measuring speed in kilometers/hour. Ex: 40 sec. is 90 km/h. (Ca 55 miles/hour). Timed over one kilometer.
The outer red numbers is km/h timed over 100 meters.
That´s what I can tell you and I´m sure someone else can tell the rest because I would also like to know.
Regards, Krister