I just noticed this. It's in bad condition but probably not beyond saving. The arm looks to be a quite rare Source Odyssey.
https://www.ebay.co.uk/itm/25583292...d=link&campid=5338728743&toolid=20001&mkevt=1
https://www.ebay.co.uk/itm/25583292...d=link&campid=5338728743&toolid=20001&mkevt=1
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