Sinclare2010, Understood on the reference to you, and I'll stick to Sinclare2010 going forward. Didn't mean to offend.
I don't use Stampsmarter (sorry Don) for much, and didn't know there was a mention of the graphite test there. I agree that oblique lighting certainly does enable ID of 95% of faint grills.
I think the difficulty in that though is, a "write-up" isn't good enough to actually teach the method. (It's like trying to teach someone by just writing a paragraph on ID'ing ribbed paper. Until I saw HOW the lighting had to work for that, I had read lots of things about it and couldn't ID them. Once I was showed the technique, then I could do it). The same holds true for this lighting and magnification method. Maybe a short video that demonstrates the technique would be more useful.
I wonder how much of this is the result of a persistent mindset within the philatelic community to "hoard knowledge". Moreso than pretty much any other "industry", save for maybe pharmaceutical.
I've worked out a method that allows clear photographing of ribbed papers. While this is a little off topic, it's similar in difficult IDing, I'm attaching the image below which compares a ribbed 162 with a typical 157.
I can't "write" how to do this, I can only show how it works.
But happy to put together a video on how this can be accomplished. It works for grills as well.