Reverend Rob
Posted March 28, 2017 - 10:53pm
Cold shouldn't make it any more likely to break, it may have just been a mainspring on its last legs. There is air inside the case, (albeit a small amount) and going from cold to warm will mean condensation due to the small amount of humidity in said air.
What this means is exactly what it says in the watch's original manual: Avoid extremes in temperature.
Sometimes this is unavaoidable as in a watch being shipped. My usual spiel is to get the watch serviced anyway if you plan to wear it. A broken mainspring usually presents no difficulties during service. Not sure what to call it yet, but it's cool.