All of my vintage subs have gen T19's but two, a rose dial Tudor that has a Clark and my recent 5512 with an SK (for now). The gens are a tiny bit clearer subjectively. The gens also seem to be more scratch and scuff resistant, but other than that...the Clark is dead on in profile and coloring. The gens average 180$ new old stock, the Clark is under 10$.The 5512 with SK is a nice crystal. but the profile is not the same as the Rolex. I prefer the genuine T19 service, but in a pinch the Clark rocks.