Huh?
My 81 H30 (same hull and basic design) has a deck stepped mast. Before I bought her, I looked at a bunch of H30s and never saw one with a keel stepped mast. Incidentally, if you mean the steel base for the compression post that lives in the bilge, this is a weak point in the design; they can rust out. Its a bit of a project to replace it. With the owner's permission, tap on it with a light hammer to see if its solid.