The car driven by Frank Sawyer does not have the mandatory CD sticker affixed to the vehicles used by the embassy personnel. The number plates are also wrong for the diplomatic use: it should have 0 (or sometimes B) followed by 17 (for US) then dash and 1 or higher. German government does issue the "American-sized" number plates which fit the narrower and taller opening on the American vehicles.
The Mercedes-Benz G-Class used as armored SWAT vehicles was introduced in 1979 and entered into the production in late 1979. The story takes place in 1978.