Aluminium disk, Kriegsmarine coastal artillery table?

[Maarten]

Friend of mine has found this aluminium disk in a Kriegsmarine coastal battery, does someone maybe
know where it was used for becouse I have no clue.
The numers count twice from 1 to 80, it probably was attached to wood.

As you can see they did some shooting on it.

[Maarten]

This one was also found with it. Maybe from the same item?