Norton fitted several types of automatic oilpumps to their engines with total-loss lubrication. Best and Lloyd pumps of the type "Mark II" (top) and "Mark IV" (bottom, with the sight window) were used; the latter was introduced in 1928 and fitted to many 1928-1929 Nortons. These pumps were made of a zinc-like metal called Mazac, also known as monkey-metal. It's fine when left alone, but overtighten a nut or screw and it breaks, and even worse, it's very difficult to repair. The "Mark V" (not shown) was introduced in 1930 and also had a sight window but was much smaller and made from aluminium. Norton never fitted Pilgrim pumps. By 1931, all these bolt-on gearpumps were displaced by the internal Norton gearpump and dry-sump lubrication.
Should you find yourself with a broken pump, there is a modern fix. You can send your broken pump to A2C2M in France (thanks, Daisuke!); they will fit your old pump's internals in a brand new body made from modern alloy stuff. It will set you back approximately 330 euro including postage.