I see a reference in here that classifies a Mark Fackeldey autoharp as rare. I have his Mark IV and it's a beauty. It has 18 bars, and a built in pickup. The downside is that it has started to develop a couple cracks on the top and one on the back and, yes, the top is showing signs of sinking. As far as its value goes, what affects it more, its rarity or its condition? Any estimates?