Many people ask us, “What is a regulator clock?” It is an excellent question, but one difficult to answer.
Even the preeminent horologist Derek Roberts admitted as much in his stunning volume Precision Pendulum Clocks: The Quest for Accurate Time Keeping. He wrote in his introduction:
“The term ‘regulator’ is such a confusing one . . . Many authorities would insist that any clock so described must have a “regulator dial layout” or, as some would say an ‘Astro,’ or Astronomical dial, by which is meant a center sweep minute hand and a separate seconds and hour rings, usually placed below 12 o’clock and above 6 o’clock . . . ”
This definition would exclude some of the finest specimens of horological history, never mind the general store, long-drop type clocks so commonly referred to as regulators. Roberts goes on:
“A further confusion can arise form the fact that the early precision clocks were called astronomical clocks because they were use din observatories, but when clocks started to be produced in England with astronomical indications on the dial, this practice was gradually discontinued to avoid confusion.”
Regulators, in a horologist’s shop, are the precision time pieces; they are the clocks that keep the most accurate, reliable time and are used to set the other clocks in the collection. Roberts writes:
“It is difficult to say wen precision timekeeping by means of a mechanical clock first occurred. “Precision” is a relative term and it may well be that the clockmakers of the late thirteenth century felt that the advent of the mechanical clock incorporating a crown wheel and folio heralded the advent of accurate timekeeping.”
In point of fact, Roberts goes on to note, these clocks were difficult to adjust, and then only by crude methods. “It is difficult to know how well these early timekeepers performed, but it seems unlikely that on average they held a rate better than five to ten minutes a day,” he goes on.
Source: Roberts, Derek. Precision Pendulum Clocks: The Quest for Accurate Time Keeping. Schiffer Publishing Ltd., 2003. Print.