Kupfer & Herrmann, Berlin

Produced cards reproducing paintings, in a long series 'Bunte Reihe', some of which list the availability of the image in bigger sizes. Some cards have a picture plus a verse/song lyrics and some just words. The initial card in this series 'Mutter' - Whistler's Mother - comes with several different address sides, including ones with the ASCO logo of Arthur Schürer, ones with just the series name and ones with the K&H logo. These have printing in the stamp box; of the ones which look like dates the earliest I have seen is 11.4.16.

Kupfer & Herrmann example
K&H BR71
K&H BR124