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type
    TBaseClass = class
               mValue:Integer;
               constructor.create(aValue);overload;
               constructor.Create(aINstance:TBaseClass);overload;  // copy Konstruktor
            end;

    TClassB = class(TBaseClass)
               constructor.Create(aInstance:TBaseClass);overload; // copy Konstruktor
            end;

    TClassC = class(TBaseClass)
               constructor.Create(aInstance:TBaseClass);overload;  // copy Konstruktor
            end;
   
var BaseList:Tlist;
    i:Integer;
    copyList:Tlist;
    Element:TBaseClass;
begin
  BaseList:=TList.Create();
  BaseList.add(TBaseClass.Create(123));
  BaseList.add(TClassB.Create(456));
  BaseList.add(TClassC.Create(789));
  ..

// und nun die Kopie der gesamten Liste erstellen
  CopyList:=TList.Create();
  for i:= 0 to BaseList.Count-1 do
  Begin
    Element:=BaseList[i]
    if Element.classtype = TBaseClass then CopyList.add(TBaseClass.Create(Element)) else
    if Element.classtype = TClassB then CopyList.add(TBaseB.Create(Element)) else
    if Element.classtype = TClassC then CopyList.add(TBaseC.Create(Element)) else
    Begin
      // error, unkown class
    end;
  end; 
End;					

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   CopyList.Add((Element.ClassType).Creat(Element)) ???