FIFA referee between 1975 and 1990, Klaus Scheurell made the made the switch from a DDR ref to a German one. He took charge of 16 European Cup matches, two matches in the 1980 Olympic Games and the last DDR cup final.
East-German team BFC Dynamo won ten Championships in a row between 1979 and 1988. They had a good team, but that wasn't the only reason. They had a honorary member who was also the head of the secret police (Stasi), a certain Erich Mielke. From documents released after 1989, it became clear Mielke used Stasi affiliated referees to make sure his team won. One of those refs who helped BFC was Klaus Scheurell. Scheurell denies this, said he made mistakes, that was all. Every ref makes mistakes.
WorldReferee's German correspondent Wolfgang tells us, one shouldn't judge too easily about these things. Helping the Stasi wasn't always a voluntary thing and someone who wanted to travel to western countries (like a FIFA referee) would have had to deal with the bad guys.