What is the value of a King George V 3 Shilling coin?

Answer 1

George III Shillings do not have holes in them.

The hole may have been bored, not at the mint, but by someone wanting to keep it with other coins on a string around the neck. I have some old British Coins with holes, obviously not part of the original design.

Any modification to a coin is very possibly illegal and makes the coin valueless as a collectible.

Answer 2

There has never been a 3 Shilling coin issued. For a brief period from 1811 to 1816, there were Bank of England King George III 3 Shilling bank tokens issued as a stop gap measure.