Believed by some to be the rarest of Rolex Explorers coupled with the fact that few people have ever seen this watch in person makes this something of a holy grail to Rolex collectors.  What makes it even more interesting is that this model didn't even have the Explorer name printed on its dial.  It is called the Rolex Space-Dweller and it was manufactured in EXTREMELY limited quantities, and only released to the Japanese market, and only on a trial-basis.Inspired by the Mercury astronauts' first visit to Japan in 1963, the watch was only produced as a test. It was said by Rolex that if the watch was acommercial success, they would then go ahead and re-brand the Explorer as the Space-Dweller solely for the Japanese market.  Needless to say as with many things, it was not a success and very few of the Space-Dwellers were produced and very few ever made into the open market.The Explorer was chosen to commemorate the astronauts' visit because they were (at the time) considered the world's greatest explorers; after all there is no greater exploration than that of space and never has been.On the odd occasion these rare little gems can be found all be it at auction from time to time and depending on the market have been known to fetch in and around $30,000-$40,000, which is amazing for what is essentially a 1016 Explorer.It really is astounding that by replacing "Explorer" with "Space-Dweller" can make this watch so sought after among collectors, when there is no technical or mechanical difference at all. The Rolex Space-Dweller is a purely emotional object of desire for most collectors and for many it will remain so .