Bader
128
Time Zone indicator
It is for pilots crossing international times zones.
Top section is 6am to 6pm
Bottom section is 6pm to 6am
Image shows the time as approaching noon.
Hope this helps

Now I understand
By: redbox : June 30th, 2021-19:27
Thanks Heiko and Steve So it looks like the 3810 and 3817 both have the 12 hour register at the 6 o'clock position and the 3815 can only count up to 60 minutes as a chrono. I guess you could count the hours on the 3815 using the bezel. Steve