Selfridge's list of German business partners contains addresses with five-digit postal codes. Postal codes were first introduced in Germany in 1941, five-digit ones not before 1993.
When German goods are removed from Selfridge's store because of World War I (1914-1918), a box with stripes in black, red and gold is to be seen. Those colors were not the ones used in Germany at that time. The colors of the German Empire (1871-1918) were black, white and red. Black, red and gold were used before 1871 and then again from 1949, when the Federal Republic of Germany was established.