About Polished Dull Nickel
Nickel is a lustrous white metal with a yellow tinge which can be polished to a high finish and is slow to tarnish
Dull nickel is the type of nickel used before 1930, and is polished to a high lustre after being plated to give a highly attractive finish.
Unlike bright nickel, which is hard, dull nickel is soft and ductile like copper. This means it's less likely to chip than bright nickel. It is also much more resistant to the weather. This is why vintage car parts are usually found to be in good condition for their age.