Mold care

[Mr. 16 gauge]

Bought a Lyman shotgun slug mold a month ago.....casts great, but now I plan on putting it away for a while. I have only had aluminum molds prior to this, so my question is:

What is the best way to treat this steel mold for long term storage? Should I oil it, or put some kind of preservative on it? What about the inside were it was cut for the bullet?

Thanks in advance..............