This is a WWII Norwegian (AT) Arbeidstjensten Labour Service gorget (ringkragen / breastshield) for “wachtoffiziere” of the Norwegian Labour Service.
Extremely rare! Only a handfull is known in collections.
On it’s original long leather band for wearing around the neck.
Very good condition, would be very hard to upgrade, that is if you ever find another!
It comes from the former Otto Spronk collection. See also the gorget book by Saris.