[jghn]

Perhaps the same documentary, but a while back I saw something where the latest techniques were easy to spot for being too good. But then they showed a new technique being developed that was able to inject natural seeming imperfections. The show claimed that this was the impetus for DeBeers laser etching their mark on diamonds as they had no other way of detecting the difference.

This was a while ago though so I'd imagine the cat & mouse game has evolved for both sides.