What an amazing photo!
The Siemensbahn was part of Berlin’s S-Bahn network from 1929 (when it was built as a short spur line to allow workers to commute to and from the Siemens factories in the area) to 1980, when it was shut down after a railway workers’ strike. As seen on the map, the Siemensbahn is the short spur line just above and to the left of the large red area in the centre.
The map is located (or was, in 2008, when the photo was taken) at the Siemensstadt station, which now lies in ruins and largely forgotten. The original poster of Flickr dates it to around 1980, probably based largely on the time the station closed. However, I date it to somewhere around 1955 to 1960 for a few reasons.
Firstly, the map is pretty much hand-drawn and lettered. A map from 1980 would look more sophisticated as printing technology improved.
Many of the outer lines are still steam-powered (cross-hatched lines are marked in the legend as “Mit Dampf…[torn]”).
While borders between West and East Berlin (as well as the Greater Berlin area) are shown, and there’s a clear colour differentiation between the two cities (blue for West Berlin, red for East), it’s still possible to travel between east and west. Each station is marked with both the time it takes to get there from Siemensstadt and the price… and these markings continue into East Berlin. Therefore, the map’s post-WWII, but before the Berlin Wall went up (1961).
Looking at old Berlin maps shows that the outer ring line around the northwest of the city was completed some time between 1955 and 1960. This line is shown on this map, although it’s hard to see because of the damage to the map: this gives the best dating I can come up with without researching individual stations. Can anyone narrow it down even more?
Another point of interest is the East Berlin station of Stalinallee, where someone has crossed out Stalin’s name and replaced it with “Frankfurter”, a reference to its pre-war name: Große Frankfurter Straße. This grafitti could have been added at anytime in the decades since the map was first put up, but the “Stalinallee” name also helps date the map, as the street was renamed as Karl-Marx-Allee in 1961.
Source: SnaPsi Сталкер/Flickr – definitely worth clicking through to the large version