A mechanical watch's timekeeping precision can be affected by interference from gadgets emitting magnetic sources, such as microwave equipment or mobile phones. To counter this, some brands house their mechanical movements inside a soft iron protective layer to repel magnetic fields.
An issue with watches showing dates is that one has to make date adjustments every other month because of the varied 30/31 day length of the months. An annual calendar is smart enough to factor for this automatically, requiring only one adjustment for February. See also: Perpetual Calendar.
A movement finishing technique whereby the edges of the component is filed and smoothened at a 45-degree angle. Often found in high-end movements.