An exceptionally rare badge here. I am unable to find another example currently for sale. This tinnie commemorates the 1927 Solidarity A.R.B. Gausportfest located in Gau 21 (Kircheim-Teck). Working pin and catch to the reverse. 
 
The Solidarity Arbeiter-Radfahrer-Bund (Workers-Cyclist Federation.) - During the Weimar Republic, the Solidarity ARB had several hundred thousand members and was the largest cycling association in the world. The S (Solidarity) signified that the ARB was a socialist organization and part of the labor movement.