As seen from below, the tourbillon base plate carries the jewel for the lower pivot of the pallet lever (1); the escape wheel pivot and pinion (2 ) (which travels around the fixed fourth wheel attached to the top plate); and the lower tourbillon pivot (3).
The top of the tourbillon base plate (4) carries the typical truncated tourbillon pallet lever (1), the escape wheel (2) and a bridge (3) to support these components. The lower balance wheel pivot is seen at (5). Because the balance pivots are inside the tourbillon pivots, cleaning and lubrication require a complete disassembly of the tourbillon assembly.
The safety roller is made of ruby, and the impulse jewel is mounted, not on a roller, but on the balance arm.
The fixed fourth wheel, around which the escape wheel pinion rotates, is visible in the bottom plate. The lower tourbillon assembly pivot sits in it's center.
As tourbillon calibers go, the 2870 is also relatively demanding of the watchmaker (and thus the owner's wallet) because of the tourbillon's very small size and the compactness of the entire movement. It is, however, an intelligently designed movement and offers surprisingly robust construction.
Like most tourbillons, the movement does not provide balance shock protection; requires disassembly of the tourbillon for service of the balance pivots; and suffers from compromised pallet lever geometry. Among contemporary tourbillons, only Blancpain has been able to solve these problems.
All that said, the 2870 is a wonderful piece, and among the small handful of truly original horological creations for the wrist. It is simply not a watch for the faint of heart or the light of pocketbook.
