In some clocks, not all, and particularly wall clocks you will find a little plaque just below the pendulum and affixed to the back panel. this is called a beat plaque or beat scale indicator.
Having a beat scale on your clock does not necessarily mean that you have a valuable clock as most were decorative but they do have a function.
In theory, the pendulum should align to the beat scale. The amplitude of the pendulum should also reveal the health of the movement. Most beat scales have I and II markers on each side of the scale. When the pendulum swings it should swing beyond the number I marker and close to the II. Having very little amplitude means investigating the movement, making pallet adjustments if necessary, or mitigating any wear issues.
A beat scale as in some high-tech clocks assumes several things; the beat scale is original to the clock, the beat scale was applied dead center, the beat scale was never removed, the case of the clock has never gone through any environmental changes (warping, high humidity, etc.), the pendulum rod and bob have never gone through the same type of environmental changes as described above, the movement, pendulum, and bob have never required any repairs or maintenance that could adversely affect the dead center between the beat scale and the pendulum, and most importantly, and the beat scale was originally designed and manufactured as a high-tech object.
Having said that, certain very high-quality clocks were produced without a beat scale, were produced with a beat scale as a guide, and, to some extent, as a decorative item.
But most beat scales are purely decorative.
Antique and Vintage Clocks 