Hi Frank,
>how does one read it btw?
Beats me! The numbers are distance in hm (hectometer), so the scale reads from 2 to 11 km.
The interval between the individual numbers increases because the projectile slows down and needs more time to cover the kilometer from 10 to 11 km than the one from 2 to 3 km.
The curved lines mean that there time to target should be indexed with a second variable, and the reading not be taken on the inside at the numbers, but at a defined distance out of the centre.
The curvature indicates that towards the rim, the projectiles slow quicker. That could indicate that the second variable was barrel elevation, as shooting straight up obviously will make the projectile slow down quicker than shooting it in a flat trajectory.
I don't know why there's a second scale - I could speculate it was etched into the glass, and the watch has a replacement glass lacking this scale. No idea!
I can't figure out the purpose of this device, either. I'd say it was for determining burst distance from observation of the projectiles and reading the elevation scale on the gun.
However, the first step in flak shooting probably is range estimation anyway, so the variable this watch could establish should already established (with greater precision) anyway.
Not that I have any idea of flak artillery procedures! :-)
Regards,
Henning (HoHun)
