Well, I finally broke down and got another Omega. It's been a little over two years since I got my first one, a Seamaster Planet Ocean. I've always been a fan of the Speedmaster, not only for its connection to the NASA space program, but also its connection to motorsports. I've been seriously looking at Speedmaster Professionals for a number of months, trying to decide whether to get vintage or new, and if new, then which one? The 3570.50.00 is the model most like the vintage ones and those worn on the moon, with a Hesalite (acrylic) crystal and solid steel caseback. The 3573.50.00 is virtually identical to the other one but features a sapphire crystal with anti-reflective coating, a sapphire exhibition caseback to view the movement, and a movement that is very slightly modified to look better (a small plastic piece is replaced with a metal one.) Ideally, I would have bought a vintage piece, probably from the late 1960s. Unfortunately, prices for excellent vintage pieces are high, and while eBay has lots of vintage Speedmasters, it's difficult to find one that is authentic, original and in good working condition without spending more than a new one. I was actually leaning towards the more "authentic" Hesalite-equipped model (what Omega refers to as the Original Moon Watch), probably because I saw it as being something closer to the vintage models I wanted, but then I realized I really wanted to see the movement and that I would probably also get a vintage one someday, and none of those have exhibition casebacks. Like my Planet Ocean, it took an excellent deal from a reputable online retailer (the same one I got my Planet Ocean from, in fact) to push me over the edge. It also happened that they had the sapphire-equipped model for less than I had planned on paying for the Hesalite-equipped model. So, I got the watch and it's fantastic. For some reason I expected the sapphire crystal to be shaped differently than the Hesalite one, but it's virtually identical. I'm also very happy with the exhibition caseback since unlike my other automatic chronographs there is no winding rotor to block the view, and I could probably spend hours just watching everything move, engage and disengage as the chronograph is started, stopped and reset. I was a little afraid that I would be disappointed with the size. If you've looked at my other watches you've seen I'm a fan of large watches, but while my Speedy Pro is smaller than my Planet Ocean (42mm vs 44.5mm diameters) it certainly does not feel small. "Sleek" might be a better word. Once again, the lack of automatic winding works well here as it is much thinner than any of my automatic chronographs. It lives up to all my expectations and I don't have any complaints.