There is a detailed exposition of East German vehicle registration plates (Autokennzeichen), with copious illustrations, at this site.  East German plates started with a group of letters, the first letter indicating the Bezirk (district) of registration:

• A - Rostock
• B - Schwerin
• C - Neubrandenburg
• D - Potsdam
• E - Frankfurt an der Oder
• F - Erfurt
• G - Cottbus
• H - Magdeburg
• I - East Berlin (Ost Berlin)
• K - Halle
• L - Erfurt
• M - Magdeburg
• N - Gera
• O - Suhl
• P - Potsdam
• R - Dresden
• S - Leipzig
• T - Karl-Marx-Stadt / Chemnitz
• U - Leipzig
• V - Halle
• X - Karl-Marx-Stadt / Chemnitz
• Y - Dresden
• Z - Cottbus