Hello La Dima, to RepGeek

Take your time searching and reading here, there's a huge store of information.
The quality of modern reps is nothing short of amazing, for example, you can see why Hublot is so determined to stop anybody from getting their hands on Big Bang reps.

Most reps use the same 316 grade satinless steel that the gens use and you really have to know your stuff to tell some reps from the real thing.