One of the qualities about Glashutte, Germany-based watchmaker A. Lange Sohne that I most admire is their dedication to refinement as well as releasing new watches. The brands fresh slogan, never stand still, (perhaps without knowing it) alludes to this attitude towards brand quality. A. Lange Sohne regularly releases updated or re-imagined versions of existing or substantially similar watches. For instance, the popularity of the Datograph later inspired the creation of the updated Datograph Up/Down, and the existence of the Datograph Perpetual Calendar has inspired the release of this arguably amazing 2016 reference 740.036F A. Lange Sohne Datograph Perpetual Tourbillon as a limited edition.The larger collection of new A. Lange Sohne watches for SIHH 2016 is extremely impressive, in my opinion, and the A. Lange Sohne Datograph Perpetual Tourbillon is just one of the many treats. Thoroughly high-end yet subtle so many of the brands enthusiast-oriented values are expressed in this deviously and deliciously complicated timepiece. It starts with a return to a concept that, for the most part, has been lost on modern luxury watches and that is displaying the tourbillon only through the caseback of the watch on the movement side. This concept isnt new for Lange, but uncommon, as I havent seen it expressed in any other models aside from the Lange 1 Tourbillon Perpetual Calendar (that also has a new version in 18k white gold for 2016). Perhaps the most popular watch that does not display its tourbillon in an exposed window on the dial is the Patek Philippe Sky Moon Tourbillon. A mere statement of tourbillon on the dial of that watch alludes to the complicated regulation mechanism within. On the dial of this A. Lange Sohne watch, the brand mentions tourbillon by stating the full name of the watch on the dial under the big date indicator where it says Datograph Perpetual Tourbillon.Interestingly enough, the A. Lange Sohne Datograph Perpetual Tourbillon isnt the only new-for-2016 A. Lange Sohne watch to have a hidden tourbillon. We also see this in a new version of the Lange 1 Tourbillon Perpetual Calendar timepiece (that I am also very fond of). More so, while it doesnt seem to be a trend, I quite like that the full name of the watch model is placed on the dial of the A. Lange Sohne Datograph Perpetual Tourbillon.If you were thinking, doesnt A. Lange Sohne already have a perpetual calendar version of the Datograph? then youd be correct. Just last year, A. Lange Sohne released a new version of the Datograph Perpetual watch (hands-on here). The message is clear: the Datograph collection is proving to be a popular seller for the brand, and they are using it as a base for exploring new and interesting movements. In the A. Lange Sohne Datograph Perpetual Tourbillon, the emphasis is on legibility and further enhancements to visual refinement as well as this gorgeous new evolution of the Datograph movement. In addition to the tourbillon regulation system, the A. Lange Sohne Datograph Perpetual Tourbillon watch has three main complication families in addition to indicating the time. The Datograph name itself implies date plus chronograph which is what the original models all had. The chronograph is column-wheel operated with a flyback mechanism and measures up to 30 minutes, sharing a minute counter subdial with some of the perpetual calendar features.Next is the perpetual calendar family of features which range from the signature big date mechanism to the moon phase indicator (which arguably exists in its own complication category). Here, we really see a fully-featured perpetual calendar complete with date, day of the week, month, and a day/night indicator. A. Lange Sohne, always meticulous about useful functionality, designed the movement with a pusher at 10 oclock which advances all of the perpetual calendar functions at the same time by one-day increments with each press of the button. This feature is extremely useful if the watch unwinds for a few days and you dont want to go to the laborious task of resetting all of the calendar functions independently. Seriously, bravo to the watch movement designers at Lange for pushing to include this feature, as they realized that someone should actually be wearing this watch and using it and not just owning it as something pretty to stare at.Last, there is a handy power reserve indicator displayed as a linear bar on the periphery of the dial between about 9 and 10 oclock. The introduction of the Datograph Up/Down brought with it a useful power reserve indicator to the mix of complications, and I applaud its presence here once again. I always say that, for me, manually wound mechanical watches really never feel complete without a power reserve indicator.So what do you think? Did A. Lange Sohne achieve their goal of designing relatively uncluttered yet inherently very data-rich dial for the A. Lange Sohne Datograph Perpetual Tourbillon? In classic Datograph style, the dial is black-colored solid silver with rhodium-plated solid gold hands. The hour and minute hands have SuperLumiNova luminant which is also something I like in these more sporty Datograph collection watches.Before discussing the details of the movement, Ill mention that the A. Lange Sohne Datograph Perpetual Tourbillon has a 41.5mm-wide case that is 14.6mm thick. This is very similar to the Datograph Up/Down and the Datograph Perpetual with just marginally more size added to the A. Lange Sohne Datograph Perpetual Tourbillon, with its roughly 1mm of added case thickness. For this initial limited edition model, A. Lange Sohne uses a solid 950 platinum case.Inside the A. Lange Sohne Datograph Perpetual Tourbillon is the in-house made A. Lange Sohne calibre L952.2 manually wound movement that comes complete with lavish amounts of hand-decoration and polishing. The movement is produced from a massive number of pieces, being assembled from a total of 729 components. Being a tourbillon watch, there is of course the diamond endstone on the balance wheel as well.A. Lange Sohne decided to design the movement to operate at 18,000 bph (2.5Hz), which is a bit slower than Id like, but it does give the watch a total power reserve of 50 hours. The original Datograph has less than 40 hours, I believe, and the Datograph Up/Down increased that to over 60. With the added complications, the 50-hour power reserve seems acceptable. Also included is A. Lange Sohnes stop-second system for the tourbillon. This uses small brake that is activated when the crown is pulled out and allows for more precise setting of the time.Attached to a matching hand-stitched black alligator strap, the A. Lange Sohne Datograph Perpetual Tourbillon has a very handsome look that easily appeals to those wanting a good-looking as well as complex timepiece. This reference 740.036F will be limited to 100 pieces and the price is 295,000. [...]