As Ian says, in the vintage years the finish on fasteners and levers, some front brake plates, etc., was dull nickel plate, there being no straight-from-the-bath bright nickel plating, however many items were polished dull nickel from new, notably radiators and exhausts. Period photos clearly show polished nickel on other items, especially on ‘show’ exhibits. I too use some polished stainless fasteners. Most grades of stainless can be slightly yellowed by heating with a blowtorch, and then it can be very difficult to distinguish from nickel plating. Conversely, polished stainless can be given the appearance of dull nickel plate by bead blasting. To prevent ‘cold welding’ of stainless bolt to stainless nut, just smear the threads with an anti-seize compound such as ‘Coppaslip’. To achieve the satin black finish on non-stainless items I use a cold gun blue solution, which is black despite the name. Earlier black finish processes had a number of trade names, like Parkerising, Bonderising, Black Japan (paint), etc.. I haven’t heard of Phil’s Brunofixing before !