Some of the advice given about spotting fakes are not correct. Not all authentic pieces have completely round links, and in the case of my titanium link necklaces, the links are clearly "pinched" together and not soldered solid. I bought them from the store on Fifth Avenue and I'm 100% sure they are authentic.
Also, I have authentic pieces with unstamped lobster claw clasps and without the small stamped circles. For instance, a plain round link chain I own has Tiffany stamped with the center circle clasp. Sometimes the hand engraving is not completely "clean" either, although machine engraving always should be.
Who wrote these anyway?