Where mortals dare not tread

My old uni lecturer brought his bike in today as the free-hub had slipped while he was out on the road, on examination it turns out that it's running on a sealed unit rather than a serviceable open unit so a new part must be ordered put the cassette back on the damaged free-hub for safe keeping then thought "I bet that's something not many people have seen before" so I took a snap of it to share with my. Blipping friends.