I don’t know if the hammer price a a reasonable one, doesn’t it?
It seems reasonable. Constantine's bronze medallions do sometimes sell for oddly low prices, but depending who bought it I also expect this may reappear soon in cleaned form, and would expect the price could at least double.
On a related note, I have this cast copy of a different medallion, RIC 279, in my collection, which is dated to Rome 326 AD same as the above one. I paid $103 for this back in 2007.
You can see the filled holes on mine, and from this I was recently able to identify the original it was copied from, which is in the Florence Archeological Museum.
What's interesting is that there have been two other cast copies of this Florence one (note same filled holes), that sold for way more money. I wonder if the buyers thought they were buying repaired originals rather than casts ?!
This one sold for $2407 in M&M 14 (2004), with the description noting the plugged holes.
This one sold for a whopping EUR 5500 in Artemide's 12-16-2006 auction.
In comparison this genuine gilt one sold for only $4800 in CNG's Triton VIII in 2005.