Identifying your 6" tags isn't too troublesome if you just compare them to other ones you have. For example, KG. He's been in every 6" line to date, so he's not an easy one to pin... but you have references to a few of the lines (I doubt you have Godzilla Island figures in the bunch anyway):
Toho Kaiju 2 - Godzilla 2000
Movie Monsters - Godzilla 1974
Movie Monsters 2006 - Godzilla 1968
Depending on which GFW Rodan that is, you may have a reference to the 2005 MM line as well. I'd definitely suggest perusing for more info.
Compare the tag styles, and you'll be able to determine each figure's origin. Good luck with your sale! If you get six-inchers I could use, I'll definitely give you a buzz (sadly, I'm not in need to too many at the moment). Don't let yourself get lowballed too much on the '74 either!
