Berlin issued this stamp on August 11, 1988 to publicize the annual meetings of the Boards of Governors of the International Monetary Fund and the World Bank Congress held in Berlin.
The global depiction appears to be a slight variation of the Werner Projection developed by Johannes Stabius round 1500. Antarctica is not shown.
From Wikipedia, "Parallels are equally spaced concentric circle arcs. Distances from the North Pole are correct as are the curved distances along parallels and distances along central meridians."