Verlag Klio, I/1, Lichtenfelsgasse 5, Wien

The logo or identification is on the address side. Some cards just have the word Klio. "Theochrom" views eg those exported to the UK have a clear image of the seated muse in a stamp-sized box at the top left. Most art cards (as the example) just have a small and indistinct version of the seated muse.

Klio 495
Klio 495 rev