Welcome to the forum, P14
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So you've got a riddle there
If as you say this 'thing' has circa 3 1/2 " as for a 6 pounder solid shot, it should weigh circa 2 600 grams (5 3/4 pounds).
If it were a howitzer ammo (bomb=grenade) should be much lighter, even if fully loaded with explosives.
But then, being a solid shot, it should (could) have a visible seam mark from the casting and, what looks to be a fuse plug ... is not.
Could you tell us more about the 'bronze' studs ? Do they appear to be 'unpluggable', or do they look definitely fixed ?
You know there are iron balls out there made for purposes other than ammo ... like windmill vane counterweights and other.
I am certain not to have helped a lot ... but i have tried hard
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