United States birth certificate numbers contain hidden information. The most obvious of which is the year of birth and State in which the birth occurred. These numbers are unique, meaning that each person has only one number even though their identity may change.
This has interesting ramifications in the case of adoptions; the adopted child has two birth certificates each with different information but the same number.
An example of how this can be useful for obtaining the identity of for adoption search. Lookup up all the children born on a certain day in a location, consult the birth index for an unnamed child born that day and in that location, match the numbers to reveal the identity of the birth mom.
The reverse is actually easier and works for birth parents searching for their lost child.
For Texas I have organized this in my People Finder. Select TX and Search up all the kids born on May 10, 1967 in Travis County, there is unnamed child certificate called “inf-of certificate” at the end. That birth certificate number will match one of the 15 kids born that day. Use my nations wide search to find the present day location each of the 15 until finding a match. (Actually click on each name to age a cross-reference with 100 other databases.) Try it free at DavidGRAYsPeopleFinder.com .