It all depends upon what your definition of original is.
Most would agree that the definition of original is that the product is and remains as it left the factory.
Most would agree that to a true collector, originality trumps everything.
In the case of the subject Parker Bros. gun that was altered from the way it left the factory by upgrading it to an A-1 Special vs. a Parker Reproduction A-1 Special, that is in as it left the factory condition, it is then obvious that only one of these guns is original. Therefore, by being original, the Parker Reproduction A-1 Special will be the greater value -- today, tomorrow and for the long haul.