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1676 horological terms explained · 10/28

Dot Over Ninety DialDial

Specific dial variant with dot marker above 90-degree position; rare configuration.

Double SealCase

Two gasket seals on crown and case back for improved water resistance.

Two superimposed chronograph hands allowing simultaneous timing of multiple independent events.

Double TourbillonComplications

Two independent tourbillons rotating in opposite directions for improved chronometric performance.

Dress WatchWatch Types

Elegant timepiece designed for formal occasions, typically thin with minimalist dial and leather strap.

Drilled lugsDesign

Lugs with holes for direct strap attachment, found on vintage military watches.

Driver's watchCase

Watch with crown positioned at 3 o'clock, designed to be worn on the right wrist for left-handed operation.

DropMovement

Angular clearance allowing pallet fork to separate from escape wheel teeth

Dual BarrelMovement

Two mainsprings in series, increases power reserve, common in chronograph movements like 9300

Dual Time ZoneComplications

Displays two different time zones simultaneously, typically with a 24-hour hand tracking second zone.

Dual-Layer Case ArchitectureCase

Hybrid watch design housing analog movement beneath integrated digital sensor layer

E-Ink Display TechnologyDial

Low-power reflective screen used in hybrid watches for extended battery life

EasylinkClasp

Quick-adjust bracelet extension system allowing rapid sizing adjustment

Easylink braceletBracelet

Rolex's quick extension system allowing additional links to be added

EbaucheManufacture

Unfinished watch movement; semi-completed base for assembly and finishing

ÉbaucheTechnical

Unfinished watch movement blank purchased by brands for assembly and finishing

Eco-DriveMovement

Citizen's light-powered technology using any light source to charge the watch indefinitely.

Elapsed Time BezelDial

Bezel starting at zero for tracking elapsed time measurement

Electrocardiogram (ECG) Electrode ArrayComplications

Dual-point electrical contact sensors measuring heart rhythm directly from wrist

Electrocardiogram (ECG) ModuleComplications

Integrated cardiac rhythm sensor for health monitoring in advanced smartwatches

ElectroplatingSurface Coating

Electrical process coating watch components with thin layers of precious metals like gold.

Elevation Gain AccumulatorComplications

Barometric pressure sensor calculating vertical ascent during hiking and stair climbing

Enamel DialDial

Porcelain-like fired coating providing smooth, durable, and lustrous finish.

End LinkBracelet

Terminal links connecting the bracelet directly to the watch lugs.

End Link GapBracelet

Visible space between bracelet end links and case lugs; increases with age.

Endlink fitDetail

Custom connection between bracelet and case lugs for improved aesthetics

Engine TurningDecoration

Mechanical engraving technique creating intricate geometric patterns using a rose engine lathe.

Engine-Turned BezelBezel

Bezel with intricate geometric pattern created using engine-turning decorative technique

Engineer braceletBracelet

Robust three-piece link construction with solid links throughout, durable and masculine

Environmental Light Spectrum AnalyzerComplications

RGB sensor detecting circadian disruption and adjusting display brightness/color temperature accordingly

Epsom LeatherStrap

Structured leather with waxy coating, rigid finish, resists water and retains shape

Equation Cam Follower Needle Wear IndexMovement

Measurement tracking point-contact wear rate on equation marchante cam surface

Equation MarchanteComplications

Moving hour hand that varies in speed to track the equation of time throughout the year.

Equation Marchante Wheel BlankTools

Pre-manufactured eccentric gear blank requiring precision grinding to equation profile

Equation Marchante Wheel Blank Inspection ProtocolCertification

Quality assurance procedure verifying eccentric gear dimensional accuracy pre-grinding

Equation of TimeComplications

Shows the difference between mean solar time and apparent solar time, ranging from -14 to +16 minutes.

Equation of Time Cam ProfileComplications

Precisely contoured mechanical cam encoding solar-sidereal time differential throughout year

Equation of Time Friction IndexMovement

Measurement quantifying friction losses in equation marchante cam follower mechanism

Equation Plate Calibration JigTools

Precision grinding fixture ensuring consistent equation of time cam profile accuracy

Equation Plate Grinding ToleranceTools

Precision specification for equation of time disc curvature deviation acceptance

Escape PinionMovement

Small pinion on escape wheel shaft that meshes with lever or pallet fork

Escape WheelMovement

Toothed wheel that delivers impulses to the balance wheel via pallet fork

Escape Wheel FrequencyMovement

Number of escape wheel teeth engaged per hour; defines movement speed and accuracy rating.

EscapementMovement

Mechanism that releases energy from the mainspring in precise, regulated pulses.

Escapement EfficiencyMovement

Energy transfer ratio from mainspring to oscillator, improved in Co-Axial and Chronergy

Escapement InspectionInspection

Close examination of escapement mechanism for wear and proper function

Escapement WheelMovement

Toothed wheel in the escapement mechanism that interacts with the lever to release energy.

ETA Caliber 2824Movement

Ubiquitous workhorse movement, 38-hour reserve, automatic, reliable and affordable

ETA Caliber 7750Movement

Legendary chronograph movement, column wheel, 42-hour reserve, widely used by luxury brands

ETA movementTechnical

Generic Swiss movement manufactured by ETA SA; widely used in affordable watchmaking

Excelsior ParkHistory

Collector authentication term for reference collection maintained by reputable vintage dealers.

Execution GradeCertification

Auction house assessment of finishing quality and assembly precision.

Execution Mark AuthenticationHistory

Collector term for verification of maker's hand-executed dial markings, scratches, and imperfections.

Exhibition casebackCase

Transparent or open caseback allowing view of the movement, common on mechanical and automatic watches.

Explorer PolarAesthetics

Explorer II with white dial, resembling polar ice fields, reference 16570.

Extract ProvenanceHistory

Auction documentation extracted from original manufacture archives confirming watch production details.

Fabric NATO StrapStrap

NATO design in woven fabric variants, breathable and casual styling option

Fabric StrapStrap

Woven textile strap often used for sport or casual watch applications.

Facet Angle ConsistencyCertification

Quality control parameter ensuring uniform cutting angles across matched gemstones.

Faded BezelCollecting and Market

Bezel with worn or faded markings from decades of use and UV exposure