Fixing A Holed Coin?

I see no way to restore that coin to a state where the filled in hole wouldn't be obvious. Keep in mind that when someone simply cleans a coin you can usually see wipe marks, especially on a coin in that condition. If you can see those there would be no way to cover up such a drastic thing as a hole.

It probably IS worth restoring such a nice coin. There are big risks involved if it is repaired by the wrong hands.

HOWEVER, the repair will still be obvious, and will do absolutely nothing to increase it's value. To some eyes, the appearance may be improved.

I would suspect that a jewler that makes his own jewlery could fix that coin fairly well. I've seen some of the items jewlers make from scratch and they look fantastic. There is an entire building I know of full of jewlery stores and companies. Many of them make their own items. I had my wifes wedding rings and charm bracelet made at one of them. I would think fixing a hole in a coin would be easy for them.
The problem is the cost. Not sure what they would charge but I would think fixing a $100 coin would cost about the same as the price of the coin.
Such fixes must not be to profitable or many jewlers would be advertising such fixes considering the coin collecting market today.
Good question though. Think I'll ask a few jewlers I know.

Actually such items are trivial to a jewler that makes jewlery all day long. The engagement ring they made for my wife was full of really small details and all made from scratch. I'm sure if such a jewler wanted to and was paid enough, it could be made almost good enough to look original. The problem like I said is the cost to do such work would cost as much as the original coin possibly.
There is a large jewlery company not far that adverises all the time that they will make anything in jewlery you want, can imagine or show them in a drawing or sketch.