If that is the address provided by Ebay when you are logged into your account, as shown in 'orders' and 'order details', then that is where you must send it.
Because the watch is going to be authenticated, that will not, in any case, be the buyer's address.
Make sure you write the whole address out correctly including the code, as that will allow the watch and the buyer and seller to be identified.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
