The serated nylon strip is the drive for the aerial - a cog drives it and it pushes the aerial up. You can sometimes buy the telescoping aerial and this drive "cable" separately (handy when some scumbag breaks off your aerial as it is a lot cheaper than the complete unit).

(list 6284, Mk1 S/N 00299 4GB blue [for sale]. Mk2 S/N 080000094 26GB blue)
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(list 6284, Mk1 S/N 00299 4GB blue [sold]. Mk2 S/N 080000094 20GB blue)