These rather clever handcuffs are not based on any particular design.  They use the hamburg 8 lock which is operated using a flatish disk pushing against the wedge shaped catch inside to release them (see picture). The internal circumference of each 'cuff is 7 1/2 inches or 9cms.  They weigh around 770 grams or 1 lb 11 ounces.  Important to know what to deduct if you weigh yourself wearing these!