Need help identifying parts in iMac 17-inch G5

Apple iMac G5 17”/1.9/512MB/160GB/SD/AP/BT: does anyone have experience in reassembling it? Two pieces has fallen out when I tried to shake the dropped screw off from the turned upside down case..... After a thorough inspection still have no idea where they came from. The first is a solid metal rectangle with something like a short axle, it has a "21" stamped in metal. The second one looks like a piece of conducting sponge. Please see pictures attached. The weird thing is that a well detailed and pictured disassembling instructions I've located on the Interned do not mention these pieces.

This iMac has a Superdrive failure, the motor does not start, the rest seems to be fine, I mean it works fine without those parts.......

Any help will be greatly appreciated. Thanks for looking!

Don't know if this will help is the rectangle magnetic at all? If so may be screen magnet.

Thanks harryb248! If it's a screen magnet where should it be put, somewhere on the LCD's back?