This is as striking of a cast iron star as I've seen, with beautiful combination of old white paint and iron rust making it feel a bit like a crustacean, having just emerged from the sea!  Iron stars like this were used in early brick building construction, functioning like giant decorative washers capping support rods that ran the width of a building. Great as an exterior ornament again, now, or hung on a wall, or as a very sturdy base for a flag on a thin post or all sorts of things.

11 7/8" across from point to point on the horizontal. Weighs 4 lb. 6 oz. Rust as evident but very sound and not actively flaking/shedding at all.