Auger electron spectroscopy (AES) was used to investigate surface films formed on copper bus bar samples installed during the years 1939–1985. The samples were collected from a telephone switching office in a heavily populated area on Long Island, with salt water located less than 5 km to the North and South. The surface films formed on the copper consisted predominantly of carbon, with smaller amounts of oxygen, chlorine and sulfur. Argon ion sputtering yielded surface profiles that were compositionally similar for all years studied. Film thicknesses varied from 10's to 100's of nanometers depending on the age of the samples. The films analysed in this study differed both chemically and in thickness from films formed on copper substrates with outdoor exposures, and from those formed in accelerated atmospheric corrosion chambers.