I believe the switch from Jack Knight to Quaife happened when the former ceased trading in 2007. That would likely leave Peter's +4 having a Jack Knight rack. Hopefully the Quaife ones although of similar design are less susceptible to the slot wear.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone