I can also recommend the Kurt Kauert publication 'Der Musikwinkel und die Harmonika' as a good source for Klingenal histories.
I got my copy in Klingenthal on one of my business trips there, it's useful but could do with being much longer, and a lot more detailed.
Another book that I find even more useful (seeing that the harmonica instrument family embraces accordions and concertinas, as well as mouth organs - indeed many manufacturers made all three!) is "
Harmonica Makers of Germany and Austria, History and Trademarks of Hohner and their Many Competitors" - especially for its seven pages of trade marks, and its ten page list of more than 250 known producers ... in the German-speaking region of Europe.
