The screw-down caseback is signed with the characteristic markings: MONTRES ROLEX SA, GENEVA, SWITZERLAND, PATENTED, and STAINLESS STEEL along with the reference number 6610. Reference: 6610. Rarity: The Reference 6610 was produced for a short period (circa 1955-1960), making it a significant and relativelyrare bridge reference between the earlier "Bubbleback" Explorers and the long-running Ref.
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