What's a Perpetual Calendar?
How is it different from an Annual Calendar or Triple-Date?
A perpetual calendar is the most developed form of the simple date window on a typical watch. It keeps track of date, day-of-the-week, (sometimes weeks), months, year, leap years, and sometimes even centuries. Because of the relatively complex rules governing the Gregorian calendar, including the varying lengths of months, and leap years every four years, a typical perpetual calendar has wheels turning from several times per second (e.g. balance wheel) all the way to once every four years. Because of the complexity of the Gregorian calendar, some perpetual calendars will require an experienced watchmaker open the watch to make an adjustment at AD 2100, or later (assuming that an experienced watchmaker still exists then).
Some less complex calendars are also available:
Semi-perpetual calendars (e.g. the Breitling Montbrilliant 1461), which requires an adjustment on leap year day only.
annual calendars (of which the Patek Philippe 5035 is an outstanding example), which only require a user adjustment once every February
"triple date" calendars, which contain month, day, and date - but need to be manually advanced at the end of each (short) month
Some would say that the inconvenience in resetting the date on a true perpetual calendar is the main reason for the existence of the watch winder industry. :-)
What's a Tourbillon?
A tourbillon is a holdover from the days of the pocket watch.
As discussed before, even for the best watches, there are small variations between the different vertical orientations (i.e. in the crown up, down, left, or right positions). This is largely due to the combined effect of gravity, the hairspring shape and attachment point on the balance staff and cock, and the regulator pins.
Unlike a wristwatch, a pocketwatch worn in a vest will spend the majority of its time in a vertical position. Therefore 18th/19th century watchmaker Abraham Louis Breguet allegedly decided that, for the absolute best accuracy, some means of balancing out the effects of gravity in the various orientations was needed. The solution he devised placed the balance wheel, escape lever, and escape wheel in a cage, which then rotated as a unit within the movement as a result of the normal escapement process. In this way, the overall effects of gravity get balanced out, as the escapement of the movement never spends any significant time in one vertical position.
However, this solution is very complex, with the result that a tourbillon has become more a statement about the watchmaker's skill rather than having any real performance advantage - starting price on a tourbillon is roughly in the $50,000 range. The performance advantage is even further nullified by the fact that wristwatches spend a less predictable amount of time in less predictable positions.
What's a Repeater?
A repeater or "Repetition Minutes" is a variety of chiming watch. Unlike a striking clock, repeaters do not automatically strike the hour, quarter, or minutes in passing - they must be activated by the user, usually through a slide or push button.
Watches which do strike "en passsant" (in passing) automatically are called Petit or Grande Sonneries.
Repeaters currently come in several varieties, based on the smallest unit of time which they can indicate:
Quarter Repeater: Chimes the hour, followed by the number of quarter-hour intervals at the current time. (example: 4:21 would have four chimes for the hours, then 1 chime for passing the first quarter-hour.)
Half-quarter Repeater: Chimes the hour, followed by the number of half-quarter hours (i.e. 7.5 minute intervals) past the hour. (example: 4:21 would have four chimes for the hours, then two chimes for two half quarters. Note that it would chime three times once getting past 4:22:30)
Five-minute Repeater: Chimes the hour, followed by the number of five-minute intervals (example: 4:21 would have four chimes for the hours, then four chimes for passing 20 minutes past the hour.)
Minute Repeaters: Chimes the hour, followed by quarter-hours, followed by minutes (example: 4:21 would have four chimes for hours, 1 chime for passing the first quarter-hour, and six chimes for minutes into the second quarter hour.)
These again are very high-priced items, with one exception - the Kelek five-minute repeater at US$5,800 (Recently sold pre-owned price in an international auction). More typically, they are in the US$20,000 and up range.
For me, I will get a repeater (instead of perpertual or tourbillion) to include in my collection . Reason???.... because not only you get visual pleasure looking at the watch, you also enjoy audio effect when the watch chimes. Best of both world!
