I bought this thinking it would be some kind of Headlock like the Tange / Suntour jobbies but turns out it's a weird little Sealed Top Nut.
8 Sided Nut with O-Ring Seal underneath and a Clear Rubber Cap up top with Printed text in Gold - Tioga - Japan - Dry & Tight - D 0.833
Never seen one before so just thought I'd share my amusement