"precise age" is a correct and usable phrase in written English.
It can be used when referring to a specific and exact age. Example: "My sister just turned 36, but she never likes to reveal her precise age."
Tree ring dating is being carried out to establish a more precise age.
He does not want his precise age published, but says he is older than he looks.
That would have allowed them to come up with a precise age using radiocarbon techniques.
Ms. Horton was in her mid-60s, but her precise age was uncertain.
It is possible that precise age has less to do with it than how often you step on a board.
Highway workers collect statistics on use by observing cars at intersections, but have no way to tell the precise age of the people they observe.
Mr. Jawad, whose precise age is unknown, has been held for nearly seven years, after first being detained as a teenager.
The Daily Mail, Daily Telegraph, Daily Express and Sun joined MP David Davies in questioning the precise age of refugees arriving in the UK.
In Congo Joseph Kabila, whose precise age has been disputed, took over from his father Laurent (who was assassinated) even though his youthful appearance was considered a handicap.
It is now clear that with recent advances the uranium lead method is superior in providing precise age information with the least number of assumptions.
It could be that Rocky the Italian Stallion, the legendary boxer he first created in 1976, is supposed to be younger than that, but no one in this film ever has the bad taste to mention his precise age.
