It doesn't, unfortunately, look like your going to get much more on this. John has pretty much put the brochure thing to rest. All I can tell you is that being the original owner of a 68 SS that came with, and still on it, the wheel covers (we have been calling them hub caps but....) are as you described in your #3: only single inner ring painted argent silver. Besides, how much better it can get than an original owner with original equipment providing you with info
..... no relying on memory or what a previous owner says was on the car when they bought it. If your still in doubt for some reason and you can think of something that I can look at on the covers or whatever then let me know and I'll have a try at it for you.