I had a mid 70's Monte Dunhill Seleccion #2 on my honeymoon. It came from about as reputable a source as there is, and I am more sure that it was stored properly than I am that I am storing MY cigars properly.
I would be very, very hesitant to buy smokes of this vintage from any but a very, very few select people.
In ISOM stock, I am becoming more and more convinced that longer aging time than most people in North america choose to allow is neccesary (for my tastes). There are, without a doubt, a number of cigars that smoke very well young, but even those benefit greatly with some age.