Hello RMW, 

Do you know why they put IIII on the coin instead of IV? Or am I misreading it?

No you are not misreading it.

Its a common but alternative in Roman to 4. Although I haven't double checked you can have a look at my Registry sets to see the same thing

You will see the William IV is the same.

4 I's.

Love that George III piece. How do you tell the difference between the originals and the restrikes?

Extremely difficult.

Forget about it if the pieces aren't Unc unless, in some cases, the dates were altered to ones not used originally by the Soho Mint.

In the mid 1800s , well after George IIIs reign, a guy by the name of Taylor managed to get a hold of original Soho Mint dies after Soho operations wound up.

Taylor used these original dies to produce restrikes.

The guru of British Copper Coinage, C Wilson Peck , produced a book on British copper and bronze Coinage and attempted to identify original early Soho , late Soho and restrike Coinage and identify minute differences between them. That book, which I have , remains as the Standard on this subject.

Many of the differences in the restrikes could be identified by wear on the original dies pressed back into service after several decades, either by lack of detail on the image produced, due to wear on the dies, by the evidence of die rust , resulting in a pebbled surface or die breaks not known in the original Coinage, in retooling or filing of the dies not known in the originals, and by other means.

Again many of these minor differences would wear away in circulated Coins but Peck consulted the British Museum and major collectors of the time to identify these differences .

Pecks book originally came out in the 1950s and was updated at least once but so far as I know remains unchallenged as the overall authority on the copper Coinage of George III. There are variants not known to Peck through further research but his book remains as the standard.

Copies are obtainable but are far from cheap. $100 plus I think for a decent copy.