Just wait until get some CMR 10 mm series. I had them to fail out of the box, cause misfiring, and even had one that causing a 2 cycle to diesel. But normally I don't much in the line plug failures.
Now the NGK that I separated from the metal shell they have been marked below the crimp ring on the ceramic body. I would have not known except I was making some pressure/vacuum adapters for testing crankcases.
