A Crown (Five Shillings) was a large coin made of silver, or in later years, copper-nickel, and of silvery appearance, approximately 38.5 mm in diameter.
A Halfpenny was a copper or bronze coin...
my prof. told us the clinical crown is what's seen by the naked eye. and the anatomical is from the end of the clinical at the Cervico Enamel Junction to the lowest point of the crown.