bruce wegmann wrote:... It comes as no real surprise to me that, given superior stability, and initally trimmed in frequency to previously unattainable precision, something as primitive as a trimmer capacitor could be dispensed with...
Well, that would be fine, but it is not the whole truth. The main reason why the trimmer capacitor disappeared is simply production cost. A trimmer is difficult to adjust automatically - and manual adjustments are way too expensive considering the total production cost of a simple watch module.
Electronic calibration as part of the production test can be a solution. This is done automatically via "test" connections on the chip. These procedures are normally not documented, so recalibration is not possible for the end user. However, I don't know if this type of ajdustment is done in any modern watch.
Standard 32kHz watch crystals have an
initial tolerance of 20ppm = 53 sec/month. Plus aging and temperature effects. Cheaper ones have 30 or even 50ppm.
I have about 30 modern digitals I keep running and wear regularly. None of them has a trimmer. They range from -2min/month to +2min/month. Most are within +/-10sec/month. The cheaper ones usually have the biggest deviation, but there are exceptions - e.g. the US$80 DKNY is more accurate than the Ventura d_sparc px which cost over 20 times more. Just a matter of luck (for the DKNY).