Hi ykl,
I have 2 Spring Drives, a GS Chrono/GMT and an Ananta GMT.
For Spring Drive technology, google as its too long to explain. I've read many articles on SD before I bought them.
Accuracy is very very good. No 100 % mechanical or even regular Quartz can beat the SDs unless its TCS.
My GS runs approx +1-1.5 sec/week(hard to see the difference between 1-1.5 but defintely under 2 secs). Surprisingly my Ananta runs even better @ <+1 sec/week although the GS is 2.5 times the cost of the Ananta.
This depends on the how the quartz crystal (that acts as a reference for the tri-syncro regulator, not actually running the quartz circuit unlike a quartz watches) is cut. There will be some minute deviation from 1 crystal to another.
SD is still totally mechanical, except for the Swiss lever escapement which is already a > 200 yrs old design like the Robin escapement.
You must be prepared to send the SD watch back to GS Japan for service as no one outside Japan has the technical knowhow. Servicing is recommended between 5-7 years for the running gears in the movt. The GS SD has 50 jewels. Some dirt will eventually build up in the moving parts over a long time...
I don't mind sending it back to Japan as my JLCs were also sent back to JLC Switzerland for service which took 2-3 months and cost RM 2-3K each time. THE GS service is in fact much cheaper @ USD 500.
