Differences Between Omega 8500a, 8500b, 8500g, 8800, 8900 Co-Axial Movements

When researching the purchase of my Omega Aqua Terra Skyfall (photographed below), one thing that greatly confused me was the caliber numbers and branding surrounding Omega’s 8000 series co-axial movements. Looking back, it seemed that I was not alone; even my local Omega AD was not able to explain the differences between confusing terms like “co-axial master chronometer” and “master co-axial chronometer” and their correspondence to caliber numbers. After researching extensively online, I think I’ve finally got it all straight (if not, correct me in the comments). Let’s go “beyond the dial” and take a look at the distinctions. …