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.
The later 275 and 330 desings reverted to the crescent-shaped aluminum tags as had been used on the earlier inside-plug 250 cars. The filter element number that is stamped in the “Tipo” block on the tags has changed from “AT4094” on the inside plug 250s to “2228.01” for the 275/330s. 275/330 crescent-shaped air cleaner tag.