I have some Norton «upright» gearboxes in the workshop now. The cases need some work, welding and milling. They have all had a hard life.
I have found some spares at different auto jumbles from time to time. The third gearbox cover, from left, I once bought in Sweden is unusual.
From left: Close ratio inter cover, “normal” Norton, mystery cover, `47 ES2 cover.
STD Norton cover.
Mystery cover marked D3T/301. I do think that it is a Norton part number. Does anybody know what it is for?