What you have is what we call a "verein" piece.
These were made for veterans of WW1 after the war to either replace a missing hat from the Great War, or to wear at reunions.
Yours would be for a former Technical Troops officer.
Is the sweatdiamond plastic or celluloid?
NEC SOLI CEDIT
Thank you for your response, I believe that it is a celluloid sweatshield.