I'm inclined to put it down as a very nice knock-off. There are some rather good knock-offs of the Vacumatic, especially from Italy. They copied the celluloid, clip, and other things quite nicely, and they are often decent pens. But there is often a different feel to the celluloid on copies. While they can be nice, but the quality isn't there. For instance the plastic is often thinner. Once you know the genuine article, when you see the copy in person, you can instantly spot the difference. Its harder from a picture.
Though very nice, there are a number of things that don't look right. The nib is from a modern Waterman Harley Davidson pen. I can't see the feed, but that could be a clue. The clip doesn't look quite right (too long and pointy), and celluloid of the blind cap is off - the lines are usually a bit more horizontal than that at the end of the barrel. I have never seen a faceted barrel on a Parker outside of the Parkettes, and I've never seen a step in the barrel like that on a Vacumatic or any other better Parker come to think of it. The Duotone may be an exception, but that was cheap injection molded plastic. Knock-offs often don't get the jewels right, and are often made to different dimensions and cheap plastic.
Is it a vacumatic filler, or is that a button at the end? It would be interesting to remove the filler and see what it looks like. Copies rarely make, or make good copies of, the Vacumatic filler system. The design is often a bit different, and the materials used cheaper metal and/or thinner, or are totally different inside.
Pretty pen though, and one that would be fun to use.