By far the most accurate watch in my collection is the Multiband6-enabled Casio G-Shock 5610. But I received the DW-291H back in December for my birthday and I had set it using the time on the 5610, it has stayed accurate ever since! Very impressive.
What's the most accurate watch in your collection that isn't radio controlled?
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I have a Bulova Lunar Pilot and the second hand on it matches the seconds exactly on my GWM5610 every time I adjust it for going on or coming off daylight savings time. I also have a new Bulova Precisionist that is to the second since I got it, but that hasn't been very long.
I have a Certina DS Action HAQ chronometer. I noticed my 5610 was a second behind my Certina one time. It turned out it hadn't received the signal for a while. Once I connected it it gained that second back and agreed with DS again. The Certina currently has lost 1 second in a little over 5 months. My favorite watch, I can just grab it and go. Also I can check all my others against it. Cheers!