totally original c. 1940's vintage american industrial single-sided porcelain enameled die cut steel "acid" danger factory sign. salvaged from an old south side chicago paint making factory. the cautionary or warning sign was likely fabricated by the ready-made sign company, new york. the sign was originally mounted against a metal fence surrounding storage tanks containing caustic materials. the nicely aged surface patina containing residual markings of the overlapping fencing add tremendous visual character. measures 14 x 10 inches. steel grommets (lining each mounting hole) remain intact.