| The Cartwheel Penny was the companion piece to the Cartwheel Twopence. Issued only in the year 1797, this copper coin measures 35mm, or 1-5/16 inches, in diameter and weighs 28.35 grams, or one ounce. The coin was minted only at the Soho Mint in Birmingham, England.
Exactly similar to the twopence, the obverse of the penny bears the image of King George III in profile. Incused (i.e. stamped, hammered, or impressed) on a raised rim around the image is the legend: GEORGIUS III . D : G . REX, meaning "George III Dei Gratia (by the grace of God) King". The reverse of the coin features an image of 'Britannia' seated on an island in the ocean (with a passing ship) and holding a trident in her left hand and an olive branch in her right. The legend incused in a raised rim around the image bears the word: BRITANNIA and the date of 1797.
The cartwheel penny was noted for two things: having been (along with the twopence) one of the first coins produced by the steam powered coin press invented by Matthew Boulton ~ and ~ by weighing exactly one ounce, could be used as a weight for measuring other products.