German props from WW1 are comparatively rare.  In good original condition they are even rarer.  This example dates from 1918 and was made for the Benz 200hp engine.  It is not possible to ascribe this prop to a particular type of aircraft but this combination of engine and prop was used on the DFW C V, Halberstadt C V, LVG C VI, and AEG J Type.

The decal is written in Sütterlin, an extreme form of Gothic script.  The Helix company was based in Berlin and made propellers for a short time at the end of WW1.