I bought DENSO Iridium TT plugs from RockAuto, part 4704, DENSO part IKH20TT. I am not overly impressed with the quality of them and have doubts about their authenticity. I emailed DENDO and they say RockAuto is not an authorized dealer. Seeing as RockAuto is a reseller, it is possible they have inadvertently resold me counterfeit parts.
There is a lot of info online about counterfeit DENSO plugs.
Things that appear authentic:
I have tried scratching the ink off the ceramic, it's baked on correctly
I have tried scratching the metal, it seems to be a quality alloy and not cheaply plated
The electrical tip appears genuine according to the various DENSO spot a fake guides
The box appears authentic, good quality printing, bar code seems ligit etc
Things that appear fake:
They have "ASSEMBLED IN US WITH FOREIGN CONTENT" stamped on them rather than "DENSO +++++++" not great quality stamping
The center ground electrode on some appears to be on a slight angle
The printing on the ceramic is slightly blurry in places and not as crisply printed as I'd expect.
Perhaps DENSO has a USA factory, and perhaps it produces a lower quality appearing product than the Japanese factory. As long as it works as well, I don't care. Given all the hype about the precision of the gap and special metals used to improve performance and longevity, the angled electrodes seem to be sloppy manufacturing and negate some of the alleged benefits of the precise tips used.
Compared to Bosch plugs I've bought in the past, these appear very cheap. I was under the impression DENSO was a high quality product and if these are genuine, I'm surprised DENSO would lower their standards.