Norton nuts and bolts

It depends on the period. Well into the 1950s, Norton were using a lot of dull chrome which is a devil of an expensive effect to copy these days (The EU seem to have outlawed the chromium salts that were used).

AMC inevitably cheapened things down and probably used cadmium (which is also now pretty-well banned except for defence contractors)

As Richard points out, the two original finishes are difficult to replicate these days. The dull chrome that Norton originally used was very durable and corrosion resistant. The nearest modern finish is satin chrome, but when used on fasteners it seems to be more brittle, i.e. it can flake off when a spanner is applied, and threads can get 'choked up' with too much plating deposit. Definitely a case of 'they don't make them like they used to'.

A good substitute for dull chrome is beadblasted stainless steel.