Rolex President bracelets are stamped with hallmarks and other markings including Rolex logo, Geneve, Swiss Made, 18K, bracelet reference number etc on the inside of the folding clasp, as shown below.
On the counterfeit bracelet, you will notice how marks and markings lose their detail when viewed under magnification. Genuine President bracelets stampings are perfect in detail and quality.
The photos below show genuine 18K white gold Rolex bracelet and fake 18K yellow gold bracelet. In this particular case, the counterfeit clasp is actually 5mm longer than a genuine one but this would be difficult to spot without having the genuine bracelet next to it. The clasp hinge cut-out is also shaped differently.
On the original clasp, the Rolex crown ( coronet ) is finely detailed.
The quality of stamping or lack of it is obvious.
In this particular case, the clasp reference number is omitted.
Note the difference in the thread of link screws.
Hallmarks: the control or inspection of precious metals was an ancient concept of examination and marking, by means of inspection stamps (punch marks). In 1424, the French Archbishop Jean de Brogny, after having consulted with a council of eight Masters Goldsmiths from Geneva, enacted a regulation on the purity and hallmarking of silver objects following the French standards for application in Geneva. Today in Switzerland only gold metal watch cases must be hallmarked. Under the current law, on all gold, silver, platinum or palladium watches cases made in Switzerland or imported into Switzerland, must bear : Maker's Responsibility Mark and his indication of purity, the official Hallmark and since 1995 the head of a Saint-Bernard dog (illustrated below). Prior to 1995. the official Swiss hallmark was a lady's head.
Finally, inside the ear of St Bernard dog there is a small letter 'g' !