I believe Rick posted info on the Nashville Session Chord Numbering system--I am not real up to date on it, meaning that I can't remember how they designate diminished, augmented chords--the one thing I think I do recollect is that when they use the "7" or VII designation, it usually means the chord based on the flatted seventh note, rather than the diatonic seventh--in key of C, it would be Bb--

I do know that, as with most musical symbol systems, there is quite a bit of lattitude--the Nashville system is intended to make it easy for the "Nashville Cats" to pick-up a tune quickly, and makes it simple to change the key, and is "quick and dirty",meaning that as little is written down as possible, problems of ambiguity are resolved by simply asking "What's this mean?"--