The last "time capsule" of Future Past was probably the plaque left by the Apollo 11 astronauts on the Moon in 1969. After all, if you're going to try to preserve something for future generations, what place is less likely to get hit by graffiti vandals than outer space? Provided you steer clear of Beta Lyra 7, that is.
When Neil Armstrong set foot upon the Moon, the world had one moment when it was gripped by the idea that it was watching real history in the making. This was something that truly had never been seen before; man had taken his first steps on another planet. It was the culmination of all the dreams of the Space Age and for some it seemed as if mankind had broken free of the Earth and was embarking at last on the great voyage into not only space, but the Future. Small wonder that when the Eagle landed it already had a memorial plaque bolted to one of the landing legs to mark the occasion. It was simple, dignified, and drove a lot of left-wingers crazy when it sunk in that Richard Nixon's signature would outlast the Pyramids. - source http://davidszondy.com/future/timecapsule/apollo.htm