These bicycle chain handcuffs are supposed to be a French design but I have not had time to research them properly.  They are a bit fiddly but the chain more easily takes the shape of the prisoners wrists because of the multiple linkages.  The internal circumference is 7 inches or 8 cms or 7 1/2 (9 cms) if you make the overlap less.  They weigh around 450 cms and are nickel plated steel