Hey David.........very intersesting post. Just from these photos, I can see the differences. My gut feeling though is that if you need to dig that deep to differentiate between them, dosen't that at least suggest that maybe you shouldn't?

My personal feeling is that these minute variations don't exhibit a desire of the manufacturer to produce a "different" chip. They are generally the result of some slight changes (some likely unintentional) in the manufacturing process.

I think, if you look hard enough, you will find numerous examples of this across the whole hobby. If we are going to argue that these "variations" make a run of chips "different", at least enough to suggest they get a seperate classification, things could get pretty darn confusing......

Just my two cents worth.........I did enjoy the post though, and the effort in investigating the
"why" of it.