The Vac 1.5s are an odd pen, which have a speedline filler and a long blind cap, but have a cap with the earlier "Standard" shape to it. Here is a photo that somewhat illustrates. At left is the first generation Standard. Second from left is a 1.5 Generation Standard. Third is the early 2nd Generation Major. Fourth is the late 2nd Generation Major.
Thank you fo the information. I do not come across many 1.5 Vacumatics and even less written information about the pen. I don’t think they are even listed in the Parker Vacumatic Book. Are you aware of any written information about the pen? When were they manufactured, between the transition time of the lock down filler and the speedline filler?