All it means is to make sure users of classified information destroy it when no longer needed, lest the info fall into enemy hands. This is typical when making information copies for official use and, when no longer needed, they must be destroyed and not simply thrown in the trash.

Nothing cryptic about it.

It's a distro panel. I've seen things like this before. Notice the red "o" and black "I" buttons in the middle. Basic on/off.

What's interesting is there are no gauges. Must've been removed for precious metal content.

probably a rifle rack for the mauser 98k, standard issue german rifle in WWII.