Alderney is one of the Channel Islands (situated in the Channel between England and France), and is part of the Bailiwick of Guernsey - a British Crown dependency. As such, it is not a sovereign country, but has operated as a quasi-sovereign entity since the Middle Ages. The island has issued commemorative coins since 1989, denominated in the Alderney Pound - which is a variant of the Pound Sterling and is legal tender on the islands, but not in the United Kingdom.
Apart from the British Royal Mint, the island has also authorised some private mints to issue coins under its jurisdiction, which come in a variety of sizes; most of them are standard, but there is also the gold £20 (twenty pounds) which is two and a half troy ounces.
The coins listed below are "Non-Circulating Legal Tender" (NCLT) and not bullion because they are issued at prices much higher than their intrinsic value, and are targeted at collectors who appreciate them for their artistic or sentimental value, and not at bullion investors.