The instrument Zimmermann depicted in his 1882 patent illustration looks nothing like an autoharp. Zimmermann likely saw one of Gutter's instruments while traveling in Europe in the early 1880's and abandoned his own patent in favor of Gutter's. Autoharps built in the USA from 1885 until the present time are identical in design to the one in Gutter's patent illustration.
-Adam Miller
Folksinging.org