Strap for Omega Speedmaster Moonwatch 310.30.42.50.01.001

The Speedmaster Professional 310.30.42.50.01.001 is the chronograph the Apollo 11 astronauts wore on 21 July 1969. This is today's version, with calibre 3861: black dial, sub-dials, tachymeter bezel, Hesalite crystal like the original. It is not a showcase watch. It is an instrument, and I treat it as one when I choose the strap.

The 3861 is a hand-wound mechanical chronograph and a certified chronometer. The case is steel, 42 mm across, water resistant to 50 metres. It measures 20 mm between the lugs and usually 16 mm at the buckle. The spring bars are 1.8 mm.

Twenty millimetres must be respected to the tenth. A wider strap forces the lugs; a narrower one leaves gaps at the sides, and the chronograph looks placed on the wrist rather than fitted. To check, put a caliper between the inner edges of the lugs: it should read 20.0.

On the Moonwatch I like box calf: it holds its shape and carries a 42 mm case. Vegetable-tanned calf takes on a patina over the years and ages with the watch. Alligator I recommend to those who wear it with a jacket. Nylon NATO is for those who use it as an instrument, at the sea too.

The black dial takes brown, dark cognac, grey and black with ease. I advise against bright colours as the only strap: they pull attention from the dial. As a second strap for the summer, though, they make sense.

You will find the 20 mm straps ready in the shop, with the buckle you prefer. If you want something built on your own wrist, with leather you choose, we make it in the atelier at Casati Milano, by appointment.