original and intact c. 1940's oversized single-sided american stamped steel reflective enameled sign purportedly used as an early form of crime scene equipment alongside the old yellow painted wood barricades and stationary beat cops. the chicago police department sign contains a reflective yellow paint field pattern with big and bold black lettering for added contrast. the more recognizable "do not cross" modern day yellow plastic tape appeared as early as the 1970's, but prior to the use of tape, signs similar to the example offered in this listing were affixed to barricades. the sign was acquired from a retired chicago detective who claimed the the sign was used on chicago crime scenes in the 1940's and 50's. great overall condition, considering age. measures 28 x 20 inches.