H. Moser & Cie. has created a unique version of its cleverly constructed, minimalist Perpetual Calendar for Only Watch 2015, featuring a black titanium case and a date disc with hand-written numerals.

One of the most original perpetual calendar movements on the market, the H. Moser & Cie. Endeavour Perpetual Calendar is clear, concise and exceptionally legible. Moser has created a one-off specimen of the perpetual with a diamond-like carbon (DLC) coated titanium case and dark grey fume dial for Only Watch 2015. The case is made of polished titanium, giving it a glossy black finish with the DLC coating. A red lacquered seconds hand and matching strap lining livens up the monochromatic colour palette.

And then there’s a thoughtful but subtle detail: because Only Watch raises funds for research into Duchenne muscular dystrophy, a disease that affects young boys, the 31 numerals on the date disc are reproductions of numerals hand-written by the children of Moser’s employees.

The HMC 341 movement inside has a seven day power reserve, as well as the Strauman Double Hairspring, two identical balance springs fitted over one another, each moving inversely to the other. Found only on limited or special edition Moser timepieces, the Double Hairspring improves timekeeping by improving the concentricity of the hairsprings’ motion.

The Endeavour Perpetual Calendar Only Watch will go under the hammer on November 7, 2015, with all proceeds raised going towards supporting research into Duchenne muscular dystrophy.