Reference 3970 was in production since circa 1987 and it was superseded by ref. 5970, released in 2004. The history of the model is somewhat more complex than other models, due to the presence of either both solid or glazed back, and then by both. To summarise, we can define the following series:
- First Series: featuring a snap-on back, either solid (3970) or glazed (3971), in production for a short time at the beginning of production
- Second series: featuring a screw-down back, either solid (3970E) or glazed (3971E)
- Third series: featuring both backs, and named simply 3970
- Fourth series: same as the third series, but featuring 7-digit movement numbers instead of the previous 6-digit one.

The present watch is a most intriguing “transitional” example of the reference, as it formally is a third series - with two casebacks - but it also presents details which are usually associated with second series timepieces. The reference number stamped on both the solid and glazed back reads 3970E, instead of the expected “simple” 3970 designation. Furthermore, it bears the hallmarks to the outside of all the four lugs, also a trait normally associated with earlier series which, beyond the historical interest, adds an ineffable layer of aesthetic appeal to the timepiece. Such hallmarks - given their highly exposed location - are extremely susceptible to polishing, especially when the case material is gold, a very soft metal. Luckily, in this instance the watch remains unpolished and the hallmarks shine in all their glory. A most interesting and appealing timepiece for the ultimate connoisseur of complicated Patek Philippe timepieces.