[Buckeye McFrog]

Too bad the article gave zero details of where the 250,000 year age came from.

Other articles say it was unearthed at a construction site in Romania in 1973.

[KarlInOhio]

So we just need to figure out the other 249,957 years.

With natural rocks you might assume that when it was formed the radioactive elements were separated from any daughter elements. Then you see the ratio of the original radioactive elements vs. newly formed daughter elements. For example, you compare radium to lead. This wouldn't work quite as well for modern alloys and doubly so after the start of the nuclear age.