Spark Plug Champion D16. T10. 18mm = SV Motorcycle = Bosh M10AC
H,J,K,WM20 Bsa. Norton 16H, Big4
all early BSA Mod.
also Sloper
please note mid war changing to:-
Champion L86c 14mm.AJS SV Models 18mmAriel SV Models 18mmMatchless SV Models 18mmVilliers Engines 98cc Midget, 98cc Deluxe, 147cc Mk 8C, 148cc Mk 12C, 15, 197cc Super Sports 18mm, 249cc MK14A, 346cc 14B, 27B