It identifies who made the knife, John Primble was just a house name for Belknap Hardware, all John Primble knives were made under contract by other knife companies.
I have seen knife books that say that those with a star were "most likely" made by Camillus prior to 1965, but to be honest I have come to doubt that Camillus is accurate and either Boker or Schrade was the correct maker.