Sheaffer Vac-Fill desk pen

[FredRydr]

I picked up this Sheaffer Vac-Fill desk pen with Triumph nib and "1050" price code from a fellow Pennsylvanian. It was offered to me with the cap as though it was part of an original set. I can't get my head around a tapered barrel with a clip cap. Though the barrel is threaded as is the cap, so is the trumpet/tulip. Where would the taper go when a desk pen is clipped in one's pocket?

Although this cap threads onto the barrel, I believe the cap is from another pen. But wonders never cease. So, if anyone has a period Sheaffer advertisement from the '40s that shows the cap is included with the desk pen and base (or even offered by Sheaffer as an accessory), I'd love to see it. Thanks!

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