Introduced in 1986 as the successor to the legendary ref. 2499, the Patek Philippe ref. 3970 marked a major evolution in the brand’s lineage of perpetual calendar chronographs. It was the first to move away from the Valjoux-based calibers used in earlier models, instead adopting a highly modified Lemania ébauche. While it retained the timeless design language of its predecessors—the 1518 and 2499—it brought new functionality to the table, including a leap year indicator and 24-hour display for the very first time.

Produced for over nearly two decades, the 3970 was offered in yellow, pink, and white gold, as well as platinum, and evolved through four distinct series.

The first series (1986–1988) featured a snap back case, feuille hands, and was only made in yellow gold—approximately 100 pieces in total.

The second series (1987–1990), like the present watch, introduced a screw-down back marked “E – Etanche,” retained the feuille hands, and was made in all four metals with around 450 examples believed to have been produced.

The third series (1989–1995) added a sapphire display back, baton hands, and lapidated indexes.

The fourth and final series (1994–2004) continued the same design with updated movement and case numbers, and later added a deployant clasp.

The present example is part of the rare second series, dating from circa 1991—among the very last produced before the introduction of the sapphire caseback. It features a platinum case with exceptionally sharp hallmarks on the lugs and a beautifully preserved dial free of blemishes. Complete with its Certificate of Origin, this 3970E is a superb representation of Patek Philippe’s technical refinement and timeless design, and a true prize for collectors of classic haute horlogerie.