Another interesting discussion are early GA pencil imprints. We know there are pencils that are imprinted Golden Arrow. However, I have two GA pen/pencil sets that are personalized with the owner's name in which the pencil has the generic "Parker" imprint. The coloring on both sets is very consistent with its partner.
Could the pencils have been added to a GA pen after the Vacuum Filler came out? Sure, but I think not. The coincidence seems just too much considering the small number of pens produced.
At any rate, the Golden Arrow/Vacuum Filler/Vacumatic evolution is a great snapshot into the business & marketing conditions at this early juncture of fountain pen history.