As with some other posts on this blog, this one may contain no information which would be new to specialists in its subject -- wristwatches, in this case -- and laypersons might ordinarily have little interest at all in the subject. Most of my posts are aimed at laypeople, and often they attempt to awaken an interest in them for something to which they'd previously barely given a thought.
On a wristwatch, a power-reserve indicator is a display on the face of the watch which shows how much longer the watch will run if it left untouched -- left unworn in the case of most contemporary high-end watches, which are automatic watches, also known as self-winding watches: they are wound by the ordinary movement of the wearer's wrist.
Or, in the case of obsessive-compulsive wearers such as myself -- I have an automatic watch: at a yard sale in 2004 I bought an automatic Timex built in 1979 for $2 -- by the unnecessarily often and frenetic shaking of the watches because we're irrationally worried that they'll run down. I think most automatic watches, including my Timex, can be wound like old-fashioned manually-winding watches, but when I wind the watch manually, it doesn't seem to stop winding when it's wound all the way, and also I'm worried that the crown -- the thing you turn to wind a watch -- may be damaged, and winding may make it worse. That, too, may well be a completely irrational worry, and yet here we are.
Maybe the power-reserve indicator was created partly with obsessive-compulsives in mind. This watch by Orient
has a maximum power reserve of 40 hours. As the watch unwinds, the hand on the dial at the bottom of the watch's face goes from right to left. In the photo, the power reserve dial is indicating that this watch will run for another 25 hours if left untouched.
40 hours is about the average maximum power reserve of a mechanical watch. If a luxury watch has a power reserve of 60 hours, the manufacturer may brag about that in a short description of the watch.
There has been a competition among some luxury watch makers to create a watch with the longest power reserve. The longest power reserve known to me is possessed by this watch by Hublot,
the Hublot Masterpiece MP-05, a manual wind-up watch, not an automatic, which can run for 50 days between windings. I'm not entirely sure what all the numbers on the face of the watch mean, but I'm guessing that the number in the upper left indicate that the watch has 40 days to go before it needs winding, and that the numbers in the upper right and at the bottom indicate that it is 9:11:30 AM or PM on the 10th of May. I could be wrong, but I'm sure it comes with an owner's manual.
When my current obsession with mechanical watches began about 3 years ago, this was the sort of watch I was not interested in. Back then, I wanted the simplest possible display: something much more like this watch by A Lange & Soehne,
the A Lange & Soehne Lange 31, also a manual wind-up, not an automatic, which happens to have an exceptional 31-day power reserve, 2nd-logest I've heard about. The dial near the 3 o'clock position in the photo shows that the watch has a little more than half of those 31 days left on its mainspring.
3 years ago, I would have liked that this A Lange & Soehne watch is made of platinum -- I still do, and I'm disappointed that the the Hublot pictured about is made of titanium -- but I would have disliked that it is a wristwatch rather than a pocket watch, and that it doesn't have bold Arabic numerals 1 through 12 marking the hours. 3 years ago, with very few exceptions such a preference for a second hand which moves in the same circle as the hour and minute hand, the more a watch's design departed from that of a 100-year-old railroad watch, the more I disliked it. So I would've detested the Hublot. However, in the past 3 years I've looked at lots and lots of pictures of extremely expensive watches, and read a fair amount about them, and gotten more and more used to, and even appreciative of, unconventional designs. Overall, I still like something like the Lange better than the Hublot, and if I could find a brand-new solid-platinum pocket watch that ran as well as a brand-new high-end wristwatch, I would like that best of all -- just letting the world's finest watchmakers know, in case they've been reading my blog, and planning to present me with a magnificent watch in appreciation of my services to the expensive-watch industry: pocket watch, platinum, size 16 or 18, as heavy as possible, cutting-edge accuracy and precision, long power reserve, and a power reserve indicator would be very nice, otherwise they don't need to go nuts with the complications or clutter up the face -- but if I were a billionaire who'd allotted several million dollars to his annual watch budget, not only would I own something like that $150,000 platinum Lange, I'd also consider shelling out $300,000 for that Hublot. (I'm not saying that either of those watches would actually spend more time on my wrist than in one of my pockets.) I don't hate the Hublot like I would have 3 years ago. I like the 50-day power reserve very much, not because I think that such a long reserve is at all necessary -- watches are no longer necessary -- but in a because-it's-there spirit. The Hublot watch is made as a tribute to Ferrari, and if I'm looking at it right, the part running from the top to the bottom down the middle of the face, besides being extremely functional, is made to look like a Formula 1 Ferrari motor.
I know more about watches than I did 3 years ago. The more you know about manufactured items the more you tend to like them, I think, all other things being equal. Some of my fellow Leftists will be appalled by this post, and consider these watches to epitomize much of what is wrong with the world, and I understand that reaction. I just disagree with it.
PS, 10 February 2017: Over at the Time Transformed website, Ambrose Lancaster has written a nice article about watches with impressive power reserves. The longest power reserve on his list is the Hublot Ferrari with 50 days, same as in this post. But he includes a few timepieces I hadn't heard of. And he writes well, and his article contains a lot of interesting information.