In an effort to provide uniform power transmission to the escapement regardless of the mainspring's state of wind, DeWitt developed their manual wound calibre DW8003, featuring a Constant Force device that utilizes a separate "Constant Force spring" located between the third wheel and the Tourbillon cage. The power released to the (flying) Tourbillon cage is always the same, as it is determined by the strength of the Constant Force spring.
The Constant Force mechanism resembles a flying regulator like in a Grand Sonnerie and consists of a spring attached to a 4-weight regulator (left of the tourbillon cage, on top the weight, below the spring). The mainspring feeds the Constant Force spring, and from there the power is transmitted via the regulator weight (it works as intertia regulator, accumulating the power; the weight is coupled to the spring by a pinion) to the Tourbillon cage every 10 seconds (thus the regulator turns six times/minute). The mechanism also serves as a shock-absorber allowing for smooth power transmission from the mainspring as it equals out the stop-go intervals of the escapement.
It is worth to note that this is not
a remontoir, as far as I understand.
It comes in a massive platinum case (water resitant to 30m) and is limited to 25 pieces. I have to say that I am not heavily in love with the massiveness (far above 40mm) of the case, which is nevertheless beautifully finished. I am sure this needs more time to appreciate is comprehensively.