21mm [1 farthing, 1 penny]. 23.5mm [1 shilling, NEW £1 coin from March 2017]. 18mm [5 pecne, 1/2 penny - small]. 31mm [1 penny - big, 50 new pence - big]. 32.5mm [1/2 crown]. 24mm [5 new pence - big].
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