I have a Norton Doll's head Gearbox for sale, as used on Nortons 1934 - 1945, 16H, Big 4, M18 etc.
Number stamped on the casting is SN84796, that would make it about 1941? (correct me if i'm wrong!)
The box is in a good condition, turns easily, switches just fine through all the gears.
Could do with a rebuild though, bearings are old.
Lugs on top are in fine condition, not/never broken off.
Complete with a kickstart and gear lever. Kickstart shaft splines are as new.
Asking price: 650 euro.
Email me for pictures if you're interested.
The SN prefix indicates the gearbox has standard ratios - hence most likely 16H. The WD Big 4s used a wide ratio gearbox and the prefix usually contained a T usually TSN. The individual pairs of gear wheels on both gearboxes added up to 42, The first pair of gear wheels on a standard gearbox were 13 and 29 - the wide ratio box first pair of gear wheels were 12 and 30. The wide ratio box used on a WD Big 4 was the same as that fitted to the 500T except for the end cover and kickstart shaft which were shortened.