It seems 'mystery' parts are quite popular these days. I've got one I've been meaning to post since I found it under the parcel shelf of my S3, along with all kinds of other discarded crap. The plastic knurled knob is on a threaded post that unscrews completely, and has a metal tension spring that presses against it. The part looks vaguely familiar to me, like I've seen one before, somewhere, sometime. I have no clue. Anyone have an idea?