- I bought a British Sovereign coins in 1904 from you, with the declared purity of 22 karats. At the same time, I inherited a few Sovereigns, coins, although they all have a purity of 18k. How can you explain this?

You should keep in mind that in the past British Sovereigns were not only minted in Britain, but also in British colonies all around the world. All the Sovereigns produced in Great Britain itself had a purity of 22k. Exactly the same low carat Sovereigns, minted in British colonies, often had a lower purity and contained less gold. For example, in Lebanon the Sovereigns only contained 72% of gold. Accordingly, these coins had a purity of 720, or slightly more than 17 carats.  
We don’t want to upset you, but we do not sell or buy British Sovereigns with a purity lower than the level specified by the Royal Mint of Great Britain - 22k. However, you can trade in your Sovereigns with a lower purity at the Bank of Greece.