Omega Seamaster 120 'Baby PloProf' 166.0250 40mm Circa 1974

Omega Seamaster 120 “Baby PloProf” Ref. 166.0250

Introduction

Produced in the 1970s, the Omega Seamaster 120 “Baby PloProf” Ref. 166.0250 is a distinctive diver’s watch that channels the bold engineering of its larger sibling, the PloProf (Plongeur Professionnel), yet in a more manageable form. With its robust case design, automatic movement, date function and utilitarian aesthetics, the model stands out in Omega’s Seamaster line as an interesting alternative to typical dive watches of its era. It brings together the garments of a serious underwater instrument with proportions and a construction that allow it to be worn more often than its professional-grade counterpart.

Historical Context of the Seamaster Line

The broader context of the Seamaster collection helps clarify why the “Baby PloProf” exists. The Seamaster line was introduced in 1948 by Omega as a water-resistant dress watch utilising the O-ring gasket innovations drawn from wartime instruments.  Over the decades, the Seamaster evolved into a full family of dive watches, culminating in large-scale professional models like the PloProf for serious underwater use. The PloProf (Ref. 600) emphasised extreme depth ratings, oversized cases and radical styling for professional divers. The Baby PloProf, in turn, can be viewed as a model designed to take much of that technical DNA and repackage it for a broader audience.

Reference 166.0250 Overview

The 166.0250 reference first appeared in the early to mid-1970s (many examples date around 1976 to 1979).  The model is often labelled the “Baby PloProf” due to its design cues reminiscent of the PloProf, especially with its tonneau or cushion-shaped case, bold hands, strong construction and diver functionality. Unlike the extreme professional PloProf models (which were large and heavy), the 166.0250 offers a more wearable size while still maintaining a solid tool-watch character.

Key specifications of the 166.0250 include a stainless steel case, automatic movement (calibre 1010), date window, and water resistance rated around 120 metres (hence the “120” in some references).  The case measurement is approximately 40mm in diameter by 42mm lug-to-lug for many examples.  These dimensions make it sizable for its era, yet more wearable than the full-scale professional dive watches of the time.

Case, Bezel and Construction

The case of the Baby PloProf is one of its most striking features. Designed with diving in mind, it is robust and angular, with strong lugs and an integrated look. Some examples list the case dimension across the bezel at 37mm but others up to 40mm; listings show 40mm x 42mm for the model.  The thickness is also substantial, reflecting the need to house a robust movement, a diver’s bezel and water-sealed case construction.

The rotating bezel is designed for elapsed-time tracking during dives. It typically features bold graduations, a notched edge for good grip even with gloves, and a strong presence on the wrist. The bracelet and strap choices reflect durability: many examples were sold on steel bracelets or integrated mesh-style bands, suitable for use in marine environments.  The screw-down caseback and crown further reinforce the diver’s credentials.

Dial and Hands

The dial of the 166.0250 often features a matte black finish, large sword or broad arrow style minute hand, and large luminous hour markers to maximise legibility underwater.  The date window at 3 o’clock adds practicality without overcrowding the dial. Many examples show well-aged patina on luminous markers and hands, adding character to this vintage piece.

One of the distinguishing features is the broad minute hand (critical for elapsed-time visibility) and the design language which emphasises utility over luxury. The dial is uncluttered and built for purpose. Notable is the fine vintage detail that the lume material may display a warm aged tone, consistent with its age and material.

Movement: Calibre 1010

The 166.0250 is powered by the Omega calibre 1010 automatic movement.  The calibre 1010 is a reliable automatic calibre from Omega for the period, featuring the date complication and holding up well over time when maintained. One listing lists the calibre as 1010, 17 jewels, running at 28,800 vibrations per hour, with a 42-hour power reserve.  

The use of an automatic calibre differentiates the Baby PloProf from many earlier manual-wind dive watches, making it more convenient for everyday wear. The robust architecture and purpose-built case construction mean that the movement is housed in a body designed to handle environmental demands.

Wearability and Practical Considerations

Whilst the model carries “professional” design cues, its size and form make it more versatile for daily wear than larger full-scale dive instruments. The case size (40 x 42mm) sits well on many wrists and offers presence without being excessively large. The strong bezel, distinctive hands and bold dive styling give it character. Many reviewers note how the Baby PloProf offers the look of a serious dive watch while being just manageable for everyday use.  

However, it is important to understand the context of its depth rating (120 metres) as opposed to ultra-deep professional ratings of the main PloProf models. While quite capable for recreational diving and water exposure, it may not match the extreme specifications of the deepest professional dive watches of the time.

Historical Significance

The Baby PloProf is significant in Omega’s history for the way it offered professional-style dive watch design in a more wearable package. It reflects a time when dive watches were evolving beyond instruments exclusively for professionals and into tools that adventurous consumers could use and appreciate. The 166.0250 sits in the transitional era of dive watch design: it carries the DNA of high-end professional models but adapts it for general use. That blending of utility and style is part of what makes it interesting from a historical perspective.

Final Thoughts

The Omega Seamaster 120 “Baby PloProf” Ref. 166.0250 is a vintage diver that bridges the gap between serious underwater instruments and accessible sports watches of its era. With robust construction, the reliable calibre 1010, distinctive design elements and wearable proportions it remains an intriguing choice for those seeking a vintage dive watch with character. From its sword-shaped hands and rotating bezel to the purposeful case construction, the 166.0250 tells the story of Omega’s dive-watch evolution in the 1970s.

While not as famous as some of its larger siblings, the “Baby PloProf” stands out as a solid example of Omega’s capabilities at that time: engineering, design and functionality intersecting in a piece that can be worn and appreciated much more often than many heavier professional-grade models. For someone looking to wear something that feels substantial, historic and distinct, the 166.0250 is a compelling option.

• Case in good vintage condition, it remains unpolished with hairlines are some pinhead chips.
• Bracelet in great vintage condition, some stretch as to be expected with age. 

Dial & hands good condition.