This more then likely doesn't mean too much, but isn't the D closer to the 9 than it is the 6 ? It's suppose to be in the middle of the 9 and 6 yes? It's off...Not by a lot, but it is off...
You are right, it is off a little. In 1964 mintmarks were still hand-punched. So it is not real uncommon to find them a little bit "misplaced". It is also rotated CCW just a bit. You are also right that it does not mean much.