Introduced in 1986, the Patek Philippe Grand Complications ref. 3970 perpetual calendar chronograph used a nearly identical aesthetic architecture of its iconic predecessors – the references 1518 and 2499. It used an all-new base movement, the caliber CH 27-70Q, which derived from the Lemania caliber 2310 – the same base movement powering early Omega Speedmasters. This was the first non-Valjoux movement Patek had ever used in a chronograph. The 3970 was sized at 36mm – a bit smaller than its direct predecessor, the ref. 2499 fourth series, which measured 37.5mm. Interestingly, the 3970’s case is larger than that of the revered 1518 (35mm) and the same size as the extremely rare and sought-after early ref. 2499s, with Vichet cases that also measure 36mm.
Like the 3940, the 3970 would add 24-hour and leap-year indications within the 9 and 3 o’clock sub-dials for improved functionality and practicality. The reference evolved over three series until it was discontinued in 2004. First-series examples with their snapback cases and feuille (leaf-shaped) hands, along with second series examples with feuille hands and screw-down casebacks, are especially attractive and rare.
Their superb quality, classic aesthetics, historical importance in the evolution of two of the brand’s most important models, and their relative affordability on the secondary market make them appealing on so many levels.