Images of the couple on the memento bear little resemblance to either the prince or his 28-year-old betrothed. Middleton appears plump in the face and lips and has bags under her eyes. Some critics claim William looks like Al Gore.
Available in silver or gold, the 5-pound ($7.70) coin marks the April 29 wedding of the second-in-line to the British throne.
Ingrid Seward of Majesty magazine told Britain's Sky News on Thursday it was "ridiculous" that the images were so poor. But Dickie Arbiter, a former royal spokesman, says it's often difficult to produce accurate images on a coin.