original and remarkably intact early 1930's salvaged chicago antique american industrial cold-rolled steel danger or cautionary single-sided "must keep out" factory machine room sign with steel grommets

original american depression era hard to find and highly sought after early danger sign comprised of heavy gauge steel with largely intact porcelain enameled finish. the single-sided danger sign was designed and fabricated by the industrial products company, philadelphia, pa. the sign contains the "universal danger signal" designed by the stonehouse steel sign company founder in 1915. the bottom stamped steel grommets remain intact. the vitreous or porcelain finish has a nicely aged surface patina. 14 X 10 inches