Strap for Perpetual Calendar 3940 Yellow Gold / Painted Roman

The Patek Philippe Grand Complications 3940J-025 has a lug width of 20 millimetres. This measurement is determined by calculating the distance between the internal attachment points of the spring bars, parallel to the case diameter. A 20-millimetre lug width is extremely widespread in the aftermarket, providing access to thousands of compatible straps in diverse materials, colourways and finishes.

For the Grand Complications 3940J-025 in 18-karat yellow gold, alligator leather in vegetable tanning is recommended, preferably in dark brown, charcoal grey or aged cognac tones. These materials enhance the technical dignity of the perpetual calendar whilst amplifying the natural patina of the yellow metal. Shell cordovan represents an extraordinary alternative for those who appreciate a decade-long chromatic evolution, whilst vegetable-tanned calf leather offers a more versatile interpretation of the model's historical complexity.

Changing the 3940J-025 strap requires the use of a spring bar tool to extract the bars. Position the watch on a soft surface, locate the lug attachments on the case, and use the tool to push a bar inward: the bar will exit the lug slot allowing you to detach the strap. Insert the new strap by reversing the process, ensuring the bar is fully locked. If unfamiliar with this procedure, consult a specialist watchmaker.

Fully compatible. The standardised lug width of 20 millimetres guarantees complete compatibility with any strap fitted with 20-millimetre bars. You may select from alligator, shell cordovan, calf, NATO, rubber and countless other leathers from both artisanal and industrial markets, without any technical or aesthetic compromise. Casati Milano produces bespoke artisanal straps for this case.

A high-quality leather strap (alligator, shell cordovan, vegetable-tanned calf) has an average lifespan of 5-8 years with conscious daily wear. Longevity depends on perspiration exposure, humidity, usage frequency and tanning quality. A vegetable-tanned strap tends to age magnificently, developing increasingly noble patina and texture, whilst structural fibre degradation typically arrives after 7-10 years. Casati Milano offers an 18-month warranty covering production defects on all artisanal straps.