Not perfect but very close: Block Berthold (Extra Condensed)

http://www.myfonts.com/fonts/berthold/block-be/extra-condensed/

Berthold's Block Condensed, designed by H. Hoffmann in 1908, has matching letter forms but is a heavier weight than the poster's heading: _Bekanntmachung_ [notice]. The Woellmer foundry produced it's own version of Hoffmann's typeface and sold it under the name of Hermes Grotesque Semi-bold. See the specimens of Block and Hermes at p255 of Jaspert's _Type Encyclopaedia [1970]_. Hermes is slightly lighter than Berthold's Block Condensed and the weight and letter widths seems to be an pretty much an exact match to _Bekanntmachung_. However, there are minor differences in the mid stroke of the letter _a_ and the arms of _k_. Hermes was digitized by by Tagir Safayev and is sold by Paratype
http://www.myfonts.com/fonts/paratype/hermes/
Paratype's Hermes would be a better match for the weight of the headline and would fit the font point size used in the poster, but Block is closer for _a_ and _k_ letter forms.
So you have a choice between two fonts with an equally Germanic Sans Serif character of the era. Either way, it seems you could have a very effective poster.
Don

Thanks bojev and donshottype for the i.d. Block Berthold (Extra Condensed) looks like a close fit!

to me it looks like hermes