A. Lange & Söhne, Glashütte i/SA, RICHARD LANGE TOURBILLON "Pour le Mèrite", Movement No. 88537, Case No. 198569, Ref. 760.025, Cal. L072.1, 41,5 mm, circa 2011

An important, extremely rare and almost as new Glashuette platinum wristwatch with regulator dial and visible tourbillon - sold out limited platinum edition no. 084 of 100 pieces - with original box
Case: platinum / sapphire glass, Lange platinum buckle. Dial: solid silver. Movm.: skeletonized 2/3 plate movement, German silver, finely executed mirror-polished steel tourbillon cage, hack feature, Glucydur screw balance.

The three-part regulator dial of the RICHARD LANGE TOURBILLON “Pour le Mérite” was inspired by a precision chronometer crafted by Dresden master watchmaker Johann Heinrich Seyffert. An inimitable feature of this timepiece is the aperture in the subsidiary-seconds dial through which the tourbillon can be observed.
An aperture in the subsidiary seconds dial exposes the steadily rotating tourbillon. To assure the unambiguous readability of the hour, a segment of the hour dial bearing the numerals VIII, IX and X flips into view at precisely 6 o’clock. It retracts again at 12 o’clock, when the pivoting dial segment is no longer needed.
The patented stop-seconds mechanism can also be observed in the dial aperture. When the crown is pulled, a V-shaped arresting spring instantly stops the tourbillon. Developed by A. Lange & Söhne, this mechanism makes it possible for the very first time to block a tourbillon in any cage orientation and regardless of the angular position of the balance. This allows the time to be set to one-second accuracy.
Source: http://www.alange-soehne.com/en/timepieces/richard-lange/#richard-lange-tourbillon-pour-le-merite/watch-gallery/158, as of 03/19/2016.