Day-Date MKIII 6511 — Red Day-Date Dial

Rolex 1055

Day and date caliberCaliberThe designation of a watch movement, identifying its design or movement family. of the first Day-Dates (6511, 6611). An improved version arrived with the 6611 in 1957; the white-gold 6611B carries a 1055B with a free-sprung balanceFree-sprung balanceA balance regulated by changing its inertia with adjustable weights or screws, while the balance spring’s active length remains fixed. It dispenses with the conventional index regulator that changes the spring’s working length. The term describes the regulating arrangement, not a particular hairspring material or certification., MicrostellaRolex’s system of small adjustable screws or nuts on the balance wheel, used to change its inertia and regulate the watch’s rate. Introduced as screws in 1957 and developed into nuts in 1983, it allows rate adjustment with the movement still cased. The name identifies the Rolex system, rather than every adjustable-inertia balance. regulation and a 0.1 mm thinner.