There seems to be quite a few fake NGK plugs about, here is how to spot them...
http://www.slideshare.net/athangal/disti...spark-plug
http://www.ngk-sparkplugs.jp/english/techinfo/fake/
http://www.slideshare.net/athangal/disti...spark-plug
http://www.ngk-sparkplugs.jp/english/techinfo/fake/