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Mass-produced#1 in family

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Top-tier supplier movement · caliber Corum Cal. CO 295: ETA 2892 base, Corum-finished, 28,800bph, 42h PR; used in Bubble Auto 47; fun convex sapphire lens focuses on the rotor · 42h power reserve
Large case: suits wrists 7 in+ (18 cm+)
47 mm case. A bold, statement-size wear. Best suited to larger wrists where the case sits flush.

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Authentication

The highly domed crystal is the defining design element of the Bubble; a flat replacement crystal changes the character of the watch entirely and is a significant value reduction.

Known issues in the market
  • The domed crystal is a proprietary Corum curve; aftermarket flat replacements are common service shortcuts.
AreaWhat to checkWhat is correctRed flag
crystalHighly domed sapphire crystalOriginal Corum highly domed sapphire crystal with correct curvature; magnifies the rotor visuallyFlat or lightly domed crystal replacement; non-genuine or aftermarket crystal swap
movementRotor visible through domed crystalAutomatic rotor visible and magnified through the domed crystal from aboveNon-genuine movement or rotor inconsistent with CO 295 specification
caseLarge 47mm case proportions47mm case with correct Bubble proportions; large and architecturalCase proportions inconsistent with 47mm Bubble specification; wrong reference
Common legitimate replacements
  • Crystal; must be Corum OEM domed sapphire only; flat crystal is wrong.
Expert resources: Corum authorized service; Corum Bubble product documentation.

Authentication guide

Last reviewed June 2026

The Bubble is named for its hemispherical domed crystal. The extreme crystal dome is the primary identifier; any claimed Bubble with a flat or mildly domed crystal is a different watch.

Known reproduction risks

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MEDIUM

Bubble replicas exist but the hemispherical crystal is expensive and difficult to source; most replicas understate the dome height.

  • Crystal dome height is the fastest check; place the watch on a flat surface and view from the side. A genuine Bubble dome extends dramatically above the case rim.
  • Porthole caseback window on replicas is often a printed image rather than actual exhibition; confirm the movement visible through the porthole has real parts that move
  • "CORUM" case engraving quality is lower on replicas

Dial variants by era

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EraDescriptionIdentifiers
2000 to present47mm steel case. Hemispherical (strongly domed) sapphire crystal. Artistic dial visible through the dome; Corum produced many limited edition dials (skulls, playing cards, portholes, abstract art). The dome distorts the dial view at extreme angles.
  • Crystal dome height is approximately 10-12mm above the case rim; significantly more domed than any other production watch
  • Viewing the dial at 45 degrees from the side shows significant optical distortion from the dome curvature; flat or lightly domed crystals will not show this
  • Case back has a porthole window showing the movement

Service part flags

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Crystal

Original: Hemispherical sapphire dome; the defining feature. Corum manufactures this crystal to proprietary specifications.

Replacement tells
  • Crystal that is less than strongly domed is a wrong replacement; even a slightly undersized dome changes the entire character of the watch
  • Scratched or chipped dome is a significant value impact; the crystal must be sourced from Corum or an authorized parts supplier
Dial

Original: Artistic dial specific to each limited edition; many are screen-printed or hand-painted under the dome.

Replacement tells
  • Mismatched dial to the reference number indicates a swap; each Bubble edition had a defined dial design
  • Water or humidity damage to the dial under the dome is a known failure mode on poorly sealed examples

Case back markings

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2000 to present
  • "CORUM" and "Swiss Made"
  • Reference and serial numbers
  • Movement designation (typically ETA 2892 or Corum-decorated ETA base)
  • Porthole exhibition window should show movement; if caseback is solid, the reference has been incorrectly serviced or replaced

Movement tells

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  • Movement is ETA 2892-A2 base with Corum decoration; some references have additional modules for complications.
  • After service, confirm the porthole caseback seals correctly; the o-ring on the porthole window is a separate seal from the caseback gasket.
  • The 47mm case size means a full-swing rotor; confirm no binding against the case wall.
Sources: Corum Bubble product page.

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