I have just been flicking through the pages on the Dr. Nicholson Collection, and i came to 1957 where it says "(For the super-specialist who is aware that there are four sub-varieties for the Calm Sea variety, this one has a Pointed 7 pointing directly at a bead, which is the commonest of the four sub-varieties.)". A while back, I was given a tin which was (and still is) full of 1957 and 1958 halfpennies... I was wondering what these 'four sub-varieties' are, and what their rarities are...