|Vibrations per hour (vph)||
This is a unit of measure for the pulse of the watch, i.e. its beat rate. In the case of a mechanical watch, it refers to how many swings/ticks the balance wheel makes in an hour. Older watches tend to have slower beat rates of 18,000 (5 ticks per second) or 21,600 vph (6 ticks per second); today’s watches typically beat at 28,800 vph, and some would be rated at 36,000 vph. Generally, the faster the beat rate, the more accurate the watch, but at the expense of greater mechanical wear and reduced power reserve.