I would be interested in trying some of those
I was taking a close look for differences between my 6060 Whte and Yellow T's. To be honest I couldn't see very much other than the "crimping hole" was slightly longer and narrower on the whites and the box edge on the yellow T's seemed to be more even (perfect) along the edge, ie. both sheets of metal ended at the same place. On the whites, the two sheets didn't appear to be quite so well aligned (no doubt cheaper!) There is no telling, of course, what's going on inside out of view either. The thing is, it all comes down to the sound and there I am more than happy with the whites (less so the yellows).
A question, what is the reason of the "engraved" writing on the plates (all mine have it too) - is it the "artist" who created it simply leaving his (or her) mark, or something more meaningful?