Hi there. I am a new member and this is my first post. I have a 1920 (King George 5th) one penny that weighs 6.8 grams; all the other similar coins that I have weighed are between 9.2 g to 9.4 g and on google it said that the regular weight is of 9.45 g. Is this a mint error? Any information will really help. Thank you!