[xkor]

вот так должна быть видна под именем Button_1:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
  private
    { Private declarations }
  public
    { Public declarations }
  published
    property Button_1: TButton read Button1 write Button1;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

end.