The present watches are from Omega's "Nuit Spatiale" or "Spatial Night" collection of split seconds chronograph watches introduced in 1966 in anticipation of the Mexico City 1968 Olympic games.
The particularities of the model are the charcoal grey case coated with non-slip enamel, preventing the watches from slipping when held in wet hands, and the black dials featuring a superimposed white chapter ring for the seconds. This characteristic combined with the extra long second hands and the anti-reflective flat crystal minimize the parallax error when reading the time.
The "Nuit Spatiale" models were also available with chronometer movements with Observatory rating certificates, the dials either with the "normal" straight Arabic numerals or, such as the present watches, with semi-centre aimed Art Deco Arabic numerals.
Another particularity of the present lot are the consecutive movement numbers of the four watches, ranging from 2324376 to 2324379, and their excellent overall condition. Obviously mainly kept in the fitted case, protecting the watches from weather while being able to time four participants of a race, the watches have remained in like new condition.
For a description and illustrations of the "Nuit Spatiale" see Omega - A Journey Through Time by Marco Richon, pp. 566 & 567.