Swage block questions

I recently saw a swage block similar to the one at the bottom of this page http://www.swageblocks.com/swage_block_gallery_d49.htm
I'd never seen this style of swage block before and I'm curious about it.
I'm guessing the large curve at the top is for repairing wagon tyres, but what would the horn be used for? It has a rounded surface and I can't think of a use for it myself.
Also the slot across the bottom of the block, the one I saw was around 12mm/.5" wide, and the depth at one end was around 50mm/2" and 75mm/3" at the other end. What would be the reason for the tapered depth?
Finally, I have a conventional blacksmiths swage block about 400mm/16" square. The outside edges are in OK condition, but the holes in the centre have badly chipped edges. I'm guessing it's been used as an anvil to be damaged that much. Is it feasible to repair the edges of the holes by welding? I've read a bit about anvil repairs, and there seem to be many different opinions about how successful it's likely to be, ranging from "totally" to "you'll ruin the anvil".
At a guess I'd suspect a lot depends on the quality of the metall the anvil was made of, as well as the skill of the person doing the repairs. A swage block should get a slightly easier life than an anvil, but does anyone what the quality of the metal is likely to be? I need to check to see whether it's cast iron or not, but beyond that is there any way to find out how well it's likely to stand up to welding and subsequent use?
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Rings come to mind, though I'm merely speculating.
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On Fri, 25 Oct 2013 20:35:57 -0400, Ecnerwal

You could be right, that's something I hadn't thought of.
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