A very fine and somewhat rare badge here, worn by memebrs of the ATSB. This badge is impressively detailed for it's small size and shows beautiful enamel work. Working pin and catch to the reverse with a very clear maker/organization mark on the pin plate. 
 
The Arbeiter-Turn- und Sportbund (ATSB or Workers' Gymnastics and Sports Federation) was a national German sports organization active between 1893-1933. The organization actively promoted leftist political views built around class struggle and nationalism.