Help Finding An Artist For An Older Patron

[librarypainter]

I work in a library and a patron brought in a painting wanting to know who the artist was. I was not sure. The artist has transcribed his name on the bottom left, but I can't read it clearly. Anyone know who painted this? I would greatly appreciate any help you could give me and the patron. Thanks!!

[librarypainter]

I'm pretty sure it's Heinrich Deiters, but I can't find this picture anywhere online.