The Omega Speedmaster Mark 4.5 is a collector nickname for reference ST 176.0012, an automatic chronograph that Omega officially archives as the Speedmaster Mark IV. The nickname reflects the watch’s Mark IV-like case design paired with the automatic calibre 1045; it is not an official Omega Mark-series name.
What is the Omega Speedmaster Mark 4.5?
“Mark 4.5” refers to the Speedmaster reference ST 176.0012. Omega’s archive identifies it as the Speedmaster Mark IV, while collectors use “Mark 4.5” for its in-between character. The term is a nickname, not a separate official model designation.
| # | Preview | Product | Price | |
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| 1 |
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Omega Speedmaster Mark II Automatic Chronograph Men's Watch 327.10.43.50.01.001 | $5,980.00 | Buy on Amazon |
| 2 |
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Omega | $8,142.00 | Buy on Amazon |
| 3 |
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Omega Speedmaster Mark II | $6,244.00 | Buy on Amazon |
| 4 |
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Omega Speedmaster Chronograph Hand Wind Black Dial Men's Watch 310.32.42.50.01.001 | $7,350.00 | Buy on Amazon |
Fratello’s 2013 account explains the nickname through the combination of Mark IV-like appearance and movement characteristics associated with the Mark V. In other words, “4.5” is a useful collector shorthand for the watch’s design and movement identity, not a number Omega assigned to a Mark-series model.
Why is it called the Mark 4.5?
The case styling recalls the Mark IV, while the watch uses automatic calibre 1045. That combination led collectors to describe ST 176.0012 as sitting between the Mark IV and Mark V in character. Fratello notes that “There never officially was a Mark 4.5,” and attributes the name to collectors.
What are the reference specifications?
Omega’s archive lists the following specifications for reference ST 176.0012:
- Official archive name: Speedmaster Mark IV
- Reference: ST 176.0012
- Collection period: 1974–1986
- Movement: automatic mechanical calibre 1045
- Functions: chronograph, day-date, 24-hour indication, and tachymeter
- Case material: stainless steel
- Water-resistance rating: 5 bar (50 metres / 167 feet)
Omega defines a 24-hour indicator as “A hand, usually on a sub-dial, which completes a rotation in 24 hours and enables the wearer to read the 24-hour time, e.g. 16:00 instead of 4 p.m.” The reference’s listed functions therefore include a way to read time on a 24-hour scale as well as its chronograph and calendar indications.
Rank #2
- Model 310.30.42.50.01.002
What does the archive’s water-resistance rating mean for a vintage example?
The 5-bar rating is a specification Omega lists for the reference; it does not establish the water resistance of a surviving watch today. Seals and other components can age, and the archive figure cannot confirm the condition of an individual example. Have a qualified watchmaker assess water resistance before exposing a vintage ST 176.0012 to water.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What should you verify on an individual watch?
Reference-level information identifies the model, but it cannot establish the authenticity, originality, condition, or service history of a particular watch. Those are unit-specific questions that call for inspection and supporting documentation.
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Rank #4
- Model 310.32.42.50.01.001
Rank #3
- Confirm that the watch and its identifying details are consistent with reference ST 176.0012.
- Ask for documentation of service history and have the movement’s condition assessed.
- Have originality and authenticity evaluated by a qualified specialist.
- Do not rely on the archive water-resistance rating as evidence that the watch remains water resistant.
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