OMEGA Speedmaster Date Original Watch Movement Calibre 1155 – Vj 7750

Omega Speedmaster Date Calibre 1155 Automatic Chronograph Movement (Valjoux 7750 Base)

Overview

The **Omega** calibre 1155 is an automatic chronograph movement based on the **Valjoux** 7750, produced between the 861/1861 and the later ETA/Dubois-Depraz calibers. Introduced in 1991, it was used in the **Speedmaster Date** line, offering a day/date function (though **Omega** omitted the day display). This movement represents a transitional period in **Omega**’s chronograph history, bridging the manual-wind 861 and the modern co-axial era.

The calibre 1155 retains the **Valjoux** 7750’s core architecture, including its cam-actuated chronograph, unidirectional automatic winding, and modular calendar system. It features 17 jewels, a lever escapement, and an Incabloc shock absorber. The finishing includes *œil-de-perdrix* circular graining on the plates and *Côtes de Genève* stripes on the oscillating weight, which is engraved with the **Omega** logo and reference.

This movement is sold as a standalone unit, without additional parts or accessories. It is functional and maintains timekeeping within expected vintage tolerances, though a full service is recommended before installation. The condition is consistent with a used movement of this era, with visible signs of handling and storage.

Specifications

The **Omega** calibre 1155 is a modified **Valjoux** 7750 with the following technical details:

Base movement: **Valjoux** 7750 automatic chronograph
Jewels: 17
Escapement: Lever, Incabloc shock protection
Balance: Monometallic, Etachron regulator with balance spring stud
Frequency: 28,800 BPH (4 Hz)
Power reserve: ~42 hours (standard for 7750 family)
Winding: Unidirectional automatic, center-mounted rotor with *Côtes de Genève* decoration
Chronograph: Cam-controlled, with 30-minute counter at 12:00 and 12-hour counter at 6:00
Small seconds: Subdial at 9:00
Date: Quickset, aperture at 3:00 (white disc with black numerals)
Day function: Present but unused in **Omega** applications (mechanism retained from 7750 base)

Plate structure: Three brass plates (calendar plate with modular components, main plate with off-center center wheel and hacking lever, top plate with winding bridge). The ratchet uses a simple bent-spring design.

Markings on the movement include:
Ω | OMEGA | 1155 (rotor engraving)
17 JEWELS | SEVENTEEN | SWISS (main plate)
7750 (base caliber designation)
ETA logo (indicating **Valjoux** 7750 lineage post-ETA acquisition)

Finishing: *Œil-de-perdrix* circular graining on plates, blued screws, and perlage on visible surfaces. The oscillating weight is decorated with *Côtes de Genève* stripes.

Notes

• The article is sold “AS IS”. A basic revision (cleaning, oiling, and timing) is recommended before use to meet manufacturer specifications.
• Any parts not explicitly mentioned in this description or not visible in the accompanying photographs are not included.
• Colors may appear slightly different across various screens and devices, so we cannot guarantee an exact screen-to-reality color match.

This calibre 1155 is a historically significant **Omega** movement, combining **Valjoux**’s robust 7750 architecture with **Omega**’s Speedmaster lineage, suitable for restoration projects or as a replacement for compatible Speedmaster Date models.