This is the quintessential Explorer reference. At 36mm wide in stainless steel with a stretch bracelet and 100m water resistance, the 1016 was launched in 1963 (what a year) and would remain in production until 1989. In 1975, Rolex updated the 1016 with a solid link bracelet (though not with solid end links) and added hacking via the new caliber 1570 movement (vs. the previous cal 1560). This where Rolex really hit its stride with the Explorer, and indeed, many of their steel sport watches.
The 1016 also gave us some seriously collectible Explorers, including the exceedingly rare “Space-Dweller.” Said to have been created for the Japanese market, little is known about this incredibly rare Explorer variant that quite literally says “Space-Dweller” on the dial and may well be one of the rarest Rolex watches ever made. Generally dated to 1965 or 1966, Ben highlighted the Space Dweller in his collecting feature for HODINKEE Magazine, Volume 3, saying, “This watch is so remarkably simple, but equally special and rare – estimates range from as few as five correct examples to at most 30 – with a small percentage seen publicly. It is the ultimate sleeper, and to me, one of the very coolest Rolex watches ever made.”
from Best Watches For Men http://bit.ly/2DyCkgP