What you have there is your basic Rosenharp. We have seen a few of these but can't find any information about them. They were made in Germany and, from all appearances, the company bought genuine autoharp parts from whoever was the current manufacturer and did the assembly in Germany.
With regard to the shifters, these were in use on some American made Autoharps made by Zimmerman from 1888 to 1892. They were also used on some Dolgeville models from 1893 to 1899, and one model made by Phonoharp from 1910 to 1918. By the time Oscar Schmidt came on the scene in 1932, shifters had disappeared but you still see them occasionally on custom made harps.
Bev and Jerry