The Seamaster 600's are very under-appreciated IMHO. They have some of the best design elements of vintage Omegas, and movements/cases of very reasonable quality and can be obtained at very reasonable pricing. They might not be super high-grade, but are very respectable nonetheless.
The answer to Art's question is that I acquired it a few months ago from a dealer. It is my only Omega (I'm mostly a vintage IWC guy), but I am a real sucker for classically simply dial design, especially when coupled with good (if not exceptional) movements. I confess to also having a preference for vintage watches that remain in exceptionally good condition, though I do very much appreciate a nice patina on certain dials.
The entire watch line that used the caliber 60x and 61x (date) have been passed over by collecting market currently. I am guessing that a lot of the collecting public really likes "beefy lugs , and thick bezel of the 1950s" . But this too will pass and more collectors will start to grab the thin case designs of the 1960s.
The caliber 600s are basically the 55x caliber automatic without the automatic winding function. They took the place of Omega's trusted and true 30 mm family of movements 30T2 , 28x, 26x series ( which Omega used from 1939 to approx 1962). The caliber 600 are also great time keepers. There is even a version caliber 602 that is a chronometer. This was the last manual wind time only chronometer till the Railmaster XXL came out a few years ago ( that is a topic of another post I am writing ).
authoratative information, and other than the properly high regard shown the 30mm movements I don't think the 600s are at all inferior.
My first Omega (& one of my first watches) is this Geneve with a Cal. 600 adjusted 2 positions, and showing many of the same styling touches of your Seamaster. It still runs and looks great, IMHO: