Beautiful, genuine Newton Aero fill cap.
Brand new, never fitted, locking, but missing key (available from Newton). Bought as a secondary body cap but just too small for my big hands - ideal
for direct tank install. 140mm OD, details in links.
Half price at £70 inc postage. U2U please.
https://www.newton-equipment.com/aero-filler-cap-range.html
https://www.speedflowshop.co.uk/aero-500-12-bolt-flange-670-512sl-1226-p.asp (ex VAT and postage !)
Probably should have cleaned the bench and put it on a red velvet cushion...