It's about 1 1/4 inches. According to a nice picture website, its Diameter: 30.81mm Weight: 9.4500g. See: http://www.treasurerealm.com/coinpapers/england/coins/S4114a.html
I have 20 British pennies, some different years in the 1960's (my son is forming a collection). Would you ( or anyone else reading this ) maybe possibly be interested in trading if you have others? ;)