reserve A,B,C,O for Ordinal,
        X for set,
        o for object,
        x,y,z,t,r,l for Surreal;
reserve n for Nat;

theorem Th48:
  x is uSurreal implies born x = born_eq x
proof
  set B=born_eq x;
  assume  x is uSurreal;
  then x = Unique_No x by Def11;
  then x in (unique_No_op B).B by Def10;
  hence thesis by Th38;
end;
