What are the dimensions, and does the hole go all the way through? The first photo looks like it may have a solid top.
If there are holes at both ends, it could well be a transformer bushing, but that's not a pattern I've seen before and typically they have more skirts closer together. I'll admit, though, that bushings are not my area of expertise. It could also be a substation piece of some type.
I don't think it's a dead end spool. The photo that Brutalfly posted doesn't show any sort of wire groove, and it doesn't match the pattern of any known dead end spool. The spools are well documented in the porcelain company catalogs.