50 Pfennig

Rheingaukreis was one of hundreds of German administrative districts forced into emergency currency production during the postwar Kleingeldnot — the acute small-change shortage that gripped Germany through 1918 and 1919 as metal coinage disappeared from circulation entirely. Carl Naumann's Frankfurt operation handled a substantial volume of this Notgeld work across the Rhine-Main region, printing for multiple issuing authorities simultaneously, which accounts for the family resemblance many of these district notes share in their typography and layout.

The 5/6 series designation in the DeNG reference indicates this is one of at least two related issues from Rheingaukreis, with the "c" suffix denoting a printing variant — likely a color or paper stock difference from the base type.