A Lister LD, LR, SL and SR valve, Lister Petter part number 201-19360.
This valve is fitted in engines as follows:-
Lister LR inlet and exhaust.
Lister LD inlet and exhaust on engines built after 1959 from engine numbers 11936LD19 & 61192LD29 (Valve 201-10363 was used on Lister LD engines built prior to 1959 up to engine numbers 11935LD19 & 6119LD29).
Lister SL exhaust.
Lister SR exhaust on engines built prior to 1970.
Approximate head diameter 29mm. Sold individually.