Unusual stuff inside computers

Hi, I recently got a very nice HP 9816 with a 9121 drive unit from Earl Baugh (thanks Earl!). The computer worked fine but the primary drive of the 9121 refused to read the disk and made a continuous beating noise. After I cleaned it on the outside I opened it to see what is wrong with it. And I found this piece inside the drive itself: http://imgur.com/dlqOexX (floppy added for size comparison). After carefully removing it, the drive actually worked like a charm and I was able to boot from it. I was pleasantly impressed that the drive head has not been damaged bumping in the leather piece all the time. I am not sure how that got there, I assume a child pushed it in by mistake? I am not sure what it is either, the leather triangles sewn together by hand it seem. What other strange pieces did you find when you opened up classic computers? Vlad.