North Dulwich Station is Grade II listed and was designed in a hybrid classical style by Charles Barry, Jr. and built in 1866 by the London, Brighton and South Coast Railway. It serves just over 0.8 million passengers a year, lies on the border of fare zones 2 and 3 and serves trains to and from London Bridge.
Just to note, the cache is fully accessible from the pavement near the station, so there's no need to enter railway property or land.
For more info on the SideTracked series of caches, please go to http://www.sidetrackedseries.info