Each chronometer also contains meteorite to symbolise the cosmos which can be seen at the centre of the hand-finished closed case back, as well as an etching of stars from the night sky in Oxford, on 8th January 1942, the date that Hawking was born. The watch’s serial number is printed on paper from original copies of a 1979 seminal research paper commonly referred to as “The ‘nuts’ and ‘bolts’ of gravity”, co-written with one of Hawking’s longest serving collaborators, Professor Gary Gibbons, that sought to understand the thermal properties of black holes.