Yes gen is on the left. Sorry I never measured my gen. Maybe you can Google or search the forum for the thickness. In saying that, I'm not sure for gen is the thickness the same for 16520 and 116520. As the 116520 uses Rolex in house movement versus the Zenith for the 16520. Since you are buying a rep of 116520, it might be better for someone here who has a gen to chime in. I will see if i can compare it to my friends one one day as I know 3 gen owners.