This postcard by Hartmann is one of many produced by Hartmann, Valentine
and others using a photograph taken during the day to create a night-time
The lighting in the windows on the left looks realistic, but the traffic
and pedestrians on Princes Street suggest that the photograph was taken at
1.35pm rather than 1.35am. See the clock tower on the North British
Railway Hotel (which incidentally was, and still is, kept a couple of
minutes fast, so that travellers are less likely to miss their trains).
This card was posted from Edinburgh to London in 1904.