[48Buick]

John:
The nickel is the underlying plating under the chrome.
When potmetal parts are chrome plated they are usualy plated in this manner.
First a strike plate to protect the potmetal from the next bath.
Then the nickel and then the chrome.
If you strip off the chrome with sandblasting, you will have gotten to the nickel. If you have pits and such in the part you will have to prime it and then go into the copper bath for some filling with the copper, then nickel and then the copy chrome.
What were you planning on filling the pits with?
48Buick