I had a bit of an unusual experience last night, when I swapped back from my 1655 to my Sub. I noticed that the Sub gained about 10 seconds in a minute, and looking at the sweep, it was noticeably faster. For a moment, I wondered if I would need to re-regulate it, then I remembered the talk about the stickng hairsprings and the 'slap fix'. I performed said slap, but left the watch on the shelf over night, just to observe it (and it is now running fine, as before) and I was thinking about what could cause a hairspring to spontaneously stick? While wearing the 1655, the sub was just left on a shelf, no electicals or speakers nearby, so I'm thinking it wasn't magnetism, maybe just the oil sticking, and I wondered how common it was for a 'sitting watch' to spontaneously do this ?