The popular Reference 3970 was produced by Patek Philippe between 1986 and 2004.
During its 18 year run, the model underwent 4 major evolutions, known as series.
The so-called 'first series', to which the present lot belongs, featured a solid snap-on case back and were made in relatively low numbers. It is thought that only as many as 100 examples of this were ever released, starting with movement number 875000.
The other three series and remaining production are also designated as 3970/E, (E suffix for étanche, or waterproof ) with the screw-down case back.
It is generally accepted that the popularity of the 3970 was down to the well balanced combination of both elegant form, heavily influenced by its predecessor the Reference 2499, and sophisticated function, with the inclusion of the chronograph and perpetual calendar complications. However as such, examples of the earlier Ref. 3970, such as the present model, are significantly rarer and less frequently seen at auction as they were made in much lower numbers.