Original: Under a transitional arrangement following reunification , between 1989 and 1993 postal codes in the west were prefixed with ` W ' , e.g. : W-1000 Berlin 30 ( postal districts in western cities were separate from the postal code ) and those in the east with ` O ' ( for Ost ) , e.g. : O-1xxx Berlin .
Simplified: There was a temporary system after reunification . Between 1989 and 1993 postal codes in the west started with W , eg W-1000 Berlin 30 ( postal districts in western cities were separate from the postal code ) and those in the east with O ( for Ost ) , eg : O-1234 Berlin .