Archaeologists have determined with a high degree of certainty that some vessels date to a particular time period. Sometimes they can narrow the range to within fifty to a hundred years. Such vessels are used to “diagnose” the strata in which they are found. See the photograph of a collar-rimmed pithos in “Excavations at Tell Mevorakh Are Prelude to Tell Dor Dig,” BAR 05:03, for a good example of a diagnostic vessel.