I think we can and should all learn something from my experience so if the forum member's will bear with me for one more post, in the interest of education I'll share what I've learned about the Omega SM 300.

First, answering the question(s) raised above -- Q: Why have a questionable watch serviced. A: Until my watchmaker showed me the problems I didn't know it wasn't kosher, just not keeping good time. That's why almost a year passed. It wasn't until the service that I knew the watch wasn't right; then I sent [name of SELLER redacted] a private email about the problem.

[SELLER] says concerns should be raised "immediately". Fair enough, though these problems weren't obvious. Those are his standards and he's entitled to set them. I know that if I were to sell something different than represented I'd play it differently. I have no problem with [SELLER] as a person; in fact, when I bought the watch I liked him enough to work hard to expedite his payment. The test, in my mind, is how one acts when things go slightly wobbly.

Anyway, back to the interesting subject of watches! :-)

Omega SM300s of this generation came in date (166.024) and non-date (165.024) versions. In this first picture, the watch under discussion is top-center. (It *is* the same watch as sold, as the one o'clock lume spot has the same tiny divot missing). Its friends are a first-gen CK-2913 1958 SM300, a 1968 non-date SM300, and another date SM300 that I bought (to make up for my mistake).

The original CK 2913 case used a caliber 500 (17 jewels) or later 501 (with 19j, later bumped to 20j).

The non-date SM300 is case reference 165.024, with movement caliber number 550 (17jewels) or 552 (24j).

The with-date SM300 is case reference 166.024, with movement caliber number 565 (24j).

The problem is clear in the side view. The top watch is [SELLER]'s SM300 and one can see the vertical face of the lug is shorter than the same face on the other date watch.

In fact the case is actually the thinner design Omega non-date 165.024 case! However, it houses a 565 movement, date-wheel and all, inside the thinner case, which can't be comfortable. The dial has to bend a bit at the edges, and the winding crown doesn't align perfectly. I doubt this is a real WatchCo work product. It may have been assembled from Omega parts, but likely not by the real (reputable) WatchCo from AUS.

So, that's what I've learned :-) It's a great hobby. Best wishes to all fellow watch enthusiasts!