Marilne-mp, I don't think "deep rust blue" has a specific meaning. To me it indicates a finish that seems t o wear better and is just a rich shade of blue. You certainly don't want to parkerize the metal unless you are just wanting something that will withstand the elements. If the rifle has been reblued before then whatever you do, within reason, should not cut the value. IL am looking forward to seeing the pictures.
Additional: I found the photos posted above after posting this reply. They are helpful in figuring out what the rifle is.