At the WatchTime show in NYC last October, we were dog-piling and pairing watches, and I noticed that my Chronomètre Souvrain was slower than the others. Having had it serviced & overhauled barely a year ago, I was concerned; so I headed for the FP Jo...
Mine is less than +1 sec/day. So you where right to bring it in. Magnetism is everywhere these days. I have bought a demagnetizer from Witschi. (I asked a Patek watchmaker at their service center, which one to get, and he recommended this one: Witschi Tes...