My impression is struck. Note the crowns were attempting to be 4 troy ounces, which is significantly heavier than the 2 avoirdupois ounces of the 1797 two pence we started with.
Please excuse my short journey into a kind of vanity if I mention I have taken the opportunity to hold in my hands both a silver crown of Charles I, and a 200 rupee piece of Aurangzeb....
Rob T