A try at automated `zip'

It's 5:00 p.m. in Manhattan. While thousands of weary commuters scurry for homeward-bound transportation, a mountain of letter mail generated by the day's business activities is just beginning its own trip through culling, facing, canceling, enriching, and sorting equipment at Manhattan's main post office on Eighth Avenue between 32nd and 33rd Streets. Much of this machinery has been operational for 10-20 years, but is still quite "new" when contrasted with postal traditions of hand labor that date from the 18th century.