This is a bit confusing...
Indeed it is confusing and is for that this fountain pen makes us think. Personally, I can ensure nothing. Just observe.
Elements contrary to VF:
1. Blind cap.
2. Nib date imprint.
3. Color appeared later.
4. Best "alignment" of celluloid that in the first vacs.
Elements for VF:
1. Barrel Imprint (by the way, curiously rare by dots absence between USA and end of PAT).
We can see that there are more elements on contrary so, although it is a mere assumption, perhaps it was cause of a peak production at the beginning (coherent with clip) of introduction of the new color and they used an oldest plate or lettering machine considering that in the '30s the users weren´t interested in imprints as collectors may be nowadays.
Footnote: regarding your thinking "I have a nice VF NIB - with the correct Blind Cap I would not Have to Golden Pearl Vacuum Filler", I think it will not be easy to find a correct golden pearl with celluloid blind cap.
Edited by Lazard 20, 15 March 2016 - 12:13.