Laser drilled diamond. The drill channels you see are not all individual channels, for the most part it's reflectionsImage courtesy of Conny Forsberg, FGA
Surface reaching fractures containing dirt have been boiled in acid for a long time in order to remove or bleach unwanted inclusions but it was 10 years after the invention of the laser that the first laser drilled diamonds started trickling into the labs. Crowningshield mentions in a 1970’s G&G article that he had heard rumors of laser drilled diamonds for several years.
A laser is used to create a tiny channel from the surface of the gem to an inclusion. When it is reached acids are used to either bleach or remove the inclusion, thus enhancing the diamonds clarity. The drill hole may or may not be filled after the removal of the inclusion has been completed.
Identification shouldn’t be too much of a problem, proper inspection with a microscope should do the trick. Note that even melée sized diamonds can be drilled so don’t just investigate the center stone of an item!