Charles, about 15 years ago, I started saving chips that I felt had a “3-D” effect, much like #6 in your example. All were H&C chips and every single one had the effect on one side only, oddly enough. There are more than we know about, I suspect, and appear to be from all over the country. Whatever was causing that effect seems to have been phased out around 10 years ago as I haven’t seen it on any new issues since then.