English Bit Levels

Anyone among us "horse riding bunch" ever seen a detailed list of bit levels & examples of each? I've found many lists that say how each level bit would fit each level of training, i.e. what a Level 1 bit does vs. a Level 3 bit; however, I've not seen good examples of each level. I know a snaffle is good for training, and I think the Kimberwick (w/ roller) my horse fancies is a level 2 or 3 (not sure which, but it ain't a 1, for sure).

Me's thinkin' there's a good book out there somewhere's, that's got all of this 'stuff information' written down. New horse lady, like my'self, I needa find me this book. :)