Hi2all, I feel silly creating a new thread for a question / topic that must have been discussed many times over, yet a Google search for "Omega Hesalite Thickness" got me nowhere... . Then I said to myself, "ha - I'm the proud owner of the Moonwatch Only book so I will look in there...". Nothing. I know that there are no less than 5 types - based on variations in the Omega symbol (or lack thereof) and that the first Speedmasters used a thicker flange for 30mm and not today's 30.8mm dials... but alas, no mention of thickness. But if anyone knows, it will be someone here I'm curious for several reasons but one is for sure a thread posted here showing a used vs. new Hesalite crystal and the height difference was impressive. If that difference is due to variance in original and service crystal, fine. If it's due to countless tubes of Polywatch... well, I'll be damned. This naturally makes me wonder if my used ('99 3572.50) Speedmaster's crystal is on the verge of disappearing... As mine uses the same version as today's, a service crystal would most likely have the same (original) thickness... . ...can't really tell how worn out it is... but thanks the to the authors of the Moonwatch Only book, I know that my crystal's not from the 60s...