Rolex

i have a friend that collects current and vintage rolex. i am contemplating buying a 1966 Pepsi dial GMT from him but it doesnt come with papers, it comes with a guarantee that all parts are original rolex. i need advice on what to do as i have never boug... 

Inside the case back, you will read the year and the quartal ( I, II, III or IV 66 ). Best, Nicolas;

i will be seeing the watch tomorrow so will get that info and post it for your review. thanks!!!