can an old watch be a luxury watch too?
Of course it can!
and Can we sell secondhand watches in your app?
If it's an authentic luxury watch, that is not stolen, then you can.
I mean a familiar old watch, that a grandfather give to their son and the father to us
If this watch fulfills the requirements mentioned earlier - then it is possible.
A watch passed down through generations isn't always an authentic luxury watch.
will somebody check their autheticity? an expert?
All timepieces have unique identification numbers, which authenticate product genuineness. These numbers are stored in the manufacturers internal databases, which we use. So, it's impossible to register a fake watch, because we have a complete database and all entered information about the watch will be amenable to further verification, as indicated in our application.