Happened to notice on the reverse of this 1920 Great Britain penny what looks like the outline of the King's head from the obverse. Poor pictures but perhaps you can see it. Is this a die clash?
I have seen this on other Goerge V large pennys, I believe it is called "Indirect Design Transfer" Lincoln Cents also show this same thing. http://www.error-ref.com/progressive-indirect-design-transfer/
Your coin is shown on this webpage.. Scroll down when you visit it http://www.error-ref.com/progressive-indirect-design-transfer/
alurid is correct. I did not know this myself until I found one of my own and thought it was a clash.