Well, the coin itself is not so surprising but more the means by which I discovered it! My copy of the September issue of Spink's Numismatic Circular arrived through the mail today. As well as my new London Mint article, it contained several London coins for sale. I skimmed through them and one caught my eye. Unlisted in RIC and not in my new list that was published only a few pages before!
So as not to spoil the fun immediately, I will leave it a few days before explaining all and illustrating the coin. No prizes for spotting which one it is, but don't bother ringing Spink as it was already sold when I made my telephone call!