I was told by Brian Baylis that these campagnolo acorn nuts are cadmium plated. Cadmium starts out looking silverish but tarnishes easily. It is superior to Zinc in protecting the nut from alkalies.
Simichrome metal polish can polish Cadmium.
Cadmium is seldom used now due to environmental concerns. Nuts, especially small ones, are often coated in a single step, which is usually Zinc or Cadmium, perhaps to avoid clogging or distorting fine threads? I am unsure.
Cadmium is superior to Zinc :
- Don Gillies
San Diego, CA, USA