These LEGO key chains are based on the Atlantis them which was introduced in 2010 whose story line is about a group of explorers that are searching the sea floor for the eponymous lost city of Atlantis from ancient myths.
Summary
Gear Key Chains / Atlantis Portal Emperor Key Chain set 852907 was released on July 4, 2010, retailing for $5, it has since been retired. New, unopened sets are valued at $7, used ones can be found for $6.
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