Can you tell me what kind of British coin this is?

Hiddendragon

I'm fairly new to coin collecting so I don't spend hundreds on pristine coins like many of you here, so forgive me if the quality of this isn't up to the usual standards. But I like old coins and I like history, so when I saw this coin from 1817 with George III on it for a very reasonable price, I had to make a bid. Now that I have it, I'd like to figure out the denomination. Most of the writing on the back is illegible. It is about the size of a quarter and I think it's silver.

Hiddendragon

This is the reverse side.

MacCrimmon

It's a George III shilling

Hiddendragon

Thanks!