Thanks for the response. The clips are plastic, and each clip is comprised of two interlocking pieces, which you can't tell from the photo. I'm as puzzled as you what they were doing in there.
Having a moisture barrier seems odd, though I wouldn't be surprised to see it employed often. Seems moisture would be more likely to by trapped by the location of the barrier (i.e. roll down wet window into metal door interior) than keeping moisture out, unless it's for general humidity in which case it would need to be nearly air tight.