Hey Martin, You know many of us that have used the V3i for a while now don't even use the analysis features anymore. I did at first but haven't in a while. Though I see your point, there does seem to be a place for it with
sale of seashells. I stopped as it just took too long but really, if one practices it shouldn't take that long.
Now, there is a guy in Germany (Reiner) who is pretty good with the V3i. He is VERY well regarded here. He says he can often tell the difference between pull tabs and gold rings using the sizing (bell curve looking) analysis screen. I know someone called him out on the forums with a post and pictures of the two analysis screens, saying Can you tell me which is the gold ring. He did...
I'll post his translated (badly) post with imagines. Perhaps by studying the broken German as well as the images you can see a difference. I spent some time (with my bad German) cleaning it up, though the last paragraph I couldn't get any better. I think he is saying there are differences but when the pull tab type changes, all bets are off. I guess just study the images but again, the images will change (e.g. pull tabs) with the type.
What I get out of the polar plot is that the 22.5 line is longer on the rings and the 7.5 line is longer on the pull tab (first image of 4 pics). Maybe this is a starting point? Or is it just because the VDI number is higher or lower for a certain freq?