Some antique cast iron was plated from the late 1800's up to the 1940's. Depending on the time frame, some were done in Nickel and some in Chrome. Typically Nickel will have a more silver look, while chrome will have a high shine. But we need to bring back that new look the best we can. We recommend a can of Easy Off oven cleaner with a yellow cap and Bar Keepers Friend.
You can spray some Easy Off oven cleaner (Lye) on the piece and place it in a bag just like the Easy Off Method on our page. This will remove the stains from carbon build up. You can use a "SOS" soap pad to scrub it clean after about 24 hours.
After using the Easy Off, you can polish it up a little more by wetting the cast iron and rubbing it with Bar Keepers Friend and a sponge. After about a minute of scrubbing, wash and dry the skillet off. The Nickel or Chrome should look a lot better now! Some of these will be missing part of the plating and that cannot be fixed with this method. Antique Vehicle restoration places can remove and re-apply the Chrome, but that cost out weighs the value of the skillet. Some cooking surfaces will be black iron and can be seasoned normally, but don't season over the plated portion! If the cooking surface is plated, don't season the skillet at all.