KN mint mark

I have been sorting through some of my coins in my fodder tin and came across a George V penny with a KN mint mark beside the date my book recognises it but gives no info about it. IGoogled it and it was made by a company called the Kings Norton Metal company in Birmingham but that is all i could find. Any info on the coin and company that made it also why they and not the Royal Mint made it would be much appreciated.

 When I saw the title I was going to write most of what I now see you already know. Also then I guess you know there were two other mints in Birmingham, England. There was Heaton and Soho.
  I remember on UK pennies in 1918 and 1919 there were three versions per year - 1918 1918H 1918KN and 1919 1919H 1919KN plus Heaton was used on quite a few Victorian pennies. More than likely that those two years were due to the end of World War I also.
  Those three mints made coins for other countries as well - such as 1923KN on this from Angola ...
https://en.numista.com/catalogue/pieces11916.html