Better known as tinnies, these were extremely popular during the Third Reich, along with WHW items, there are over 12,000 listed in one of my reference books alone. I'll start off with my 1934 May Day (RVP21) tinnie. These were issued on the 1st May every year from 1934-1939. The early tinnies had Tag der Arbeit (Day of Work/Labour Day) on the badge, as well as the date, and were produced by large numbers of firms. Many were marked on the rear with the maker, many were not. This one was produced by Reichsverband Pforzheim No21.
Hello from sunny Port Macquarie