TPQp90 A robust estimate of an assemblage TPQ based on the 90th percentile of the beginning manufacturing dates for all the artifacts comprising it. If the TPQp90 of an assemblage is 1770, then 90 percent of the artifacts in the assemblage have a beginning manufacturing date before 1770. This measure is less sensitive to excavation errors and taphonomic processes that might introduce a small amount of anomalously late material into an assemblage.