This is a blue aluminum tag, “AEC 103A”, (40x100mm) used on the Dinoplex units on the Daytona coupes. It warns against loosening the battery cables when the engine is running. Blue AEC 103 A Dinoplex tag for Dayonas
The earliest Ferraris used a simple hand former aluminum scoop. The later 166s had a cast aluminum “Ram’s horn” assembly with a louvered aluminum can at each end. This assembly was made by the Weber carburetor company in Bologna. Most of the aluminum castings have a small tag riveted to the top surface at the center. Some did not. The very early street cars used only a single carburetor but this configuration was soon changed to the more familiar three carburetor set-up. Early Weber “Ram’s horn” air cleaner tag.