Omega’s Speedmaster Mark series – like this full serviced 1973 Mark IV Ref. 176.0009 here, on its original Omega-sgned bracelet and with Omega box and papers – was Omega’s attempt to follow the immense success of its Omega Speedmaster Professional line of Moon watches, in particular following the its 1969 presence on the Moon and the bragging rights that followed (and continue to this day).
 
Omega decided to come up with a successor to fit design trends of the 1970s, thus giving birth to the Omega Speedmaster Professional Mark line, beginning with the Mark II - to include the Mark IV here.  Per Fratello, "The Omega Speedmaster Mark series is a very exciting one. Some fans say that no collection is complete without them, others frown upon the thought of owning any."
 
"Again, others look at them as novelty watches of a bygone era. Remainders of a time when Omega was experimenting with various technical improvements.  Regardless of which group we belong to one thing is for certain; the Omega Mark watches mark an era (no pun intended) in the history of the Speedmaster."
 
Unlike the Speedmaster Professional, the Mark series featured barrel-shaped cases, polished chamfers, and a brushed top and sides, giving it a rather different look from the standard Speedmaster Professional case worn by NASA astronauts.  The classic Speedmaster tachymeter the Professional is famous for is also different – instead of residing in an external bezel, it is under the mineral glass crystal, protecting the tachymeter from scratches or disruption.
 
Specifically concerning the Speedmaster Mark IV, Omega debuted the reference in 1973.  Despite its "IV" nomenclature, the IV was the third Mark in line (not including the 145.022, which some consider the Mark I) - regardless, the IV was only the second Speedmaster to feature the quite legendary Calibre 1040, Omega’s first automatic chronograph movement based on the equally legendary Lemania 1340.
 
Regrettably, Omega only marketed the Mark IV for a handful of years; in circa 1974-75 the company debuted a newer version, the ref. 176.012, aka the Mark 4.5 - the 4.5 was collector originated, given it features elements of both its predecessor and successor, the Mark IV and Mark V, respectively.
 
Now, for some a little on the legendary Speedmaster pedigree.  Omega introduced its Speedmaster line of chronographs in 1957, when it was introduced as a sports and racing chronograph, complementing Omega's position as the official timekeeper for the Olympic Games.
 
The manual winding Speedmaster Professional or "Moonwatch" is the best-known and longest-produced; it was worn during the first American spacewalk as part of NASA's Gemini 4 mission and the first watch worn by an astronaut walking on the Moon during the Apollo 11 mission.  The Professional remains one of several watches qualified by NASA for spaceflight and is still the only one so qualified for EVA.  The Speedmaster line included other models, including analog-digital and automatic mechanical watches.
 
Beginning in 1962, NASA – anticipating the need for astronauts on space missions to move about in space outside the ship, thus necessitating the need for a wristwatch to withstand the difficult conditions of space – anonymously purchased a series of chronographs from different watch brands in an effort to find the best watch available for astronauts to wear in space.
 
In 1964, the watches satisfying all pre-requirements were officially purchased by NASA and subjected to a series of tests and pre-selection processes called the “Qualification Test Procedures.”  The three remaining were subjected to 11 different tests – some of the most rigorous trials endured in the history of horology.  By early March 1965, testing was complete, leaving – you guessed it – only the Speedmaster.
 
On 20 July 1969, the first manned lunar landing resulted in NASA astronaut Neil Armstrong as the first to step onto the Moon’s surface.  As the electronic timing system on the Lunar Module was malfunctioning, Armstrong left his watch aboard as a reliable backup.  Nearly 20 minutes after his first step, he was joined by Buzz Aldrin wearing his Omega Speedmaster Professional – making the Speedmaster the first watch worn on the Moon.  Alas, a few months after this mission, Buzz's watch was stolen, and remains missing to this day.
 
From here, the Speedmaster steadily gained a reputation of a reliable and historic timepiece – since the epic first steps on the Moon, the Speedmaster Professional remains the only NASA-qualified watch for extravehicular activity (EVA).
 
This Speedmaster Mark IV comes on its original Omega-signed bracelet, and with nylon strap, leather-backed canvas strap, springbar tool, and rugged travel case.  It also comes with Omega inner/outer boxes and instruction manual.