Following Omega's participation in the Apollo missions, the brand expanded the Speedmaster line with variants known commonly as the "Mark" Series - one of the most polarizing lines among today's Omega disciples.

The Speedmaster Professional is perhaps the most distinctive chronograph in all of horology (second only perhaps to the ). This is due in part to a sound design language that has remained relatively unchanged since the 1950s. So when Omega decided to expand the Speedmaster line, they couldn't have made a more distinctive (and some say divisive) choice.

Though met with a varied reception from Speedmaster purists, the 'Marks' represent a fascinating off-shoot in design and functionality that has given rise to a cult collector following today. Of all Omega's Mark designs the Mark III is perhaps the most innovative--not just aesthetically, but technically as well. 

Like its immediate predecessor, the Mark II, the Mark III was drenched in a decidedly '70s design language.  The chunky steel 'helmet' case and hidden-lugs are emblematic of the era and represent to some the beginning of the big watch phenomenon. The Mark III, introduced in 1971, is powered by the Caliber 1040. The Calibre 1040, patented in 1970, was Omega's first automatic chronograph caliber. This came close on the heels of the three-way tie for the first automatic chronograph movement--the , the , and the Seiko 6139.

Developed in conjunction with Lemania (who produced the legendary Caliber .321 and .861 that powered the Apollo-era Speedmasters), the Caliber 1040 featured a quick-set date function at 3:00, a running seconds subsidiary dial with incorporated 24-hour indicator at 9:00, and a 12-hour register at 6:00 and a central minute counter hand (topped with its distinct orange 'plane'). 

As was the case with all the Mark watches, Omega offered the the Mark III with a variety of dial and case configurations (including, quite bafflingly, a variant in solid 18k gold). This expression features the same exact blue dial that Omega in the popular  Chronograph line. 

But the most distinctive feature of the Mark III is of course the case. To put it bluntly, this watch is huge: while the diameter may only be 41mm, the case is thick, nearly 16mm. It's hefty, sturdy, the kind of watch you can't forget you're wearing.

No one else will, either.