History

Certain career/role insignia were worn by specialist soldiers performing certain unique tasks. All ranks below Lieutenant could qualify for these specialist trades.
The time of introduction varied greatly between the different insignia.
Since 1939, NCO insignia came with a silver-coloured band around the edges.

A Fortress Construction Sergeant (Festungsbaufeldwebel) wore a yellow Gothic “Fb” on a round dark blue-green backing.