Nivada Grenchen Chronomaster Aviator Sea Diver 85004 / 3730

The Ref. 85004 / 3730 marks a significant technical evolution in the Chronomaster family, produced in the late 1960s and early 1970s. Its primary importance lies in the use of the highly respected Valjoux 23 movement. This caliber is a manually wound, column-wheel chronograph, considered a more refined and technically superior mechanism to the cam-actuated Valjoux 92 found in the preceding reference. While retaining the classic 38mm stainless steel “straight-lug” case and the highly functional dual-scale bezel, this reference represents the pinnacle of the classic Chronomaster design paired with a high-grade movement. Visually, these models are very similar to their immediate predecessors, typically featuring baton hands and the established “Chronomaster Aviator Sea Diver” dial layout. Dials from this era will feature a “T SWISS T” marking at the bottom, indicating the use of tritium for luminescence. The dual reference number, 85004 / 3730, is a specific quirk of this model, likely used to denote the specific combination of case and the new Valjoux 23 movement. For many collectors, this reference is the most desirable of the manually-wound Chronomasters due to its sophisticated movement.