The size and shape of the bowl changed over time, making it a useful tool for dating. Harrington, who worked at Jamestown, looked at bowls that still had part or all of the pipe stem attached.
These measures can refine TPQs by removing ceramic outliers that may have been introduced through excavation error or disturbance.
The clay pipe industry expanded rapidly as tobacco smoking gained popularity in both England and America. Harrington studied the thousands of pipe stems excavated at Jamestown and other colonial Virginia sites, noticing a definite relationship between the diameter of the pipe stem bore—or hole—and the age of the pipe of which it had been part.
Although an object may have a known manufacturing date, this does not mean that the object was used when it was made. A hand-me-down set of dishes you inherited when you went to college?
A known manufacturing date tells us that the site cannot be older than the object, but that doesn’t mean that the site is not a lot younger. The presence of these things can throw off the mean ceramic date. In an ideal world, every deposit would contain a dated penny.
Sadly, the majority of artifacts are not stamped with their date of manufacture.