I like Bar Keeper's Friend.

I find they come off very well with a microfiber cloth or a Mr. Clean Magic Sponge.

Gloria

I'm not looking for another abrasive cleaner. Comet works well at this. I got the impression from reading other comments that there are things to use that will not damage the surface of the ceramic over the years. For example regular Clorox removes veggie stains. What takes the steel marks off?

Wenol metal cleaner will work for your sink. It is non-abrasive.

I've used it on vintage pottery and it was wonderful. Vintage car owners use one variety for the chrome on their cars.

Per the Russel Wright guru this would be a first choice to remove metal marks.....Corelle stovetop cleaner a second.

Check that auction site if you can't find any locally. It goes a long way too.

HTH,
wing