As of 6/16/14 Update, Dunna has been ninja editted to also have Geomancy +5 (straight buff) on the Bell. Was doing some tests, getting +10 refresh from Indi/Geo Refresh spells with Dunna and Nepote on. It looks like the +5 Geomancy is a straight buff, meaning, this Bell just got dangerously better for GEO!
JSE augment update from February 2016 added MP/Magic Accuracy/Fast cast augments to Dunna. Word is 300 beits/boulders/plutons to r15 and while unconfirmed, my own current progress seems to hint at it. Cycle through all his chat options and select About the weapons... to gain access to JSE augments. You may in fact augment JSE while working on RME progress. Once you start with one type of RME mat you must use it the entire way.