My VW1000's serial number is in the 200 range. When you are watching 3D using it, tilting your head to the side (so one ear or the other is closer to the ground--in other words, tilting, not turning, your head) causes the colors to shift markedly. I had talked to Sony Tech Support about this a few months back. A few weeks ago, I got a phone call from them, telling me they were sending me out a filter to correct for it. It is a square filter in a metal springy bracket that snaps easily over the front of the lens, still allowing room for the cover to close properly.
The filter appears completely clear to the naked eye, so much so that, once I removed the plastic sheets protecting it, I had to touch the corner of it to ensure there was actually something there.
The filter, when snapped in place, is not beautiful, but what it does to the 3D picture is: Not only did it completely eliminate the color shift, it increased the brightness a little and deepened the contrast a great deal: When testing it, the half of the picture I was not holding the filter in front of looked dim and washed-out, as well as color-shifted. Very impressive! I could see no difference at all in the picture watching 2D content with no glasses, so having it in place all the time is not a problem (other than the fact that it spoils the looks of our beautiful projectors when looking directly at the lens, but, then, we're the only ones who ever do that).
The filter stands off from the front glass of the lens, so dust will not be "trapped" between the two surfaces, although, obviously, having another lens sitting in front with two exposed surfaces means more dust-collection surfaces. Fortunately, it snaps off as easily as it snaps on, making cleaning simple.
There are no part numbers anywhere on the assembly, nor were there any instructions. The assembly just naturally snaps over the front of the lens, though, so installation couldn't be easier. It is possible to have it rotated 90 degrees off, in which case the 3D is actually worse. Just make sure that the two little tabs that stick out are on the sides, not top and bottom, and you'll be fine.
If, when watching 3D, tilting your head does not cause a really obvious color shift, with faces turning from brown to blue, you don't need this filter. If it does, you do.