Strap for Perpetual Calendar Chronograph 3990 Platinum / Black Diamond

The lug width of the Patek Philippe 3990P-029 is 18 millimetres. This dimension represents the internal distance between the two lugs of the case and is crucial when selecting a compatible strap. A different lug width would cause mechanical stress on the pins and aesthetic imbalance. All straps offered by Milano Straps for this size have been tested to ensure precise and secure fit.

For a Grand Complication in platinum, Nile alligator represents the ideal choice: its fine natural grain, mechanical resistance and sophisticated aesthetics create perfect visual harmony with the case. Vegetable-tanned calf offers a more informal alternative, with a patina that evolves over time. Shell cordovan is the choice for those who appreciate constructive excellence and desire superior structural rigidity. Your decision depends on your personal style and primary context of use.

Changing the strap requires specific tools: a spring bar tool and gentle pressure on the elastic bars (spring bars) that hold the strap to the case lugs. The procedure: (1) insert the tool into the lug opening; (2) apply gentle pressure to create space; (3) pull the strap outward; (4) repeat from the other side. Reverse the procedure to install the new strap. For a Patek Philippe, we recommend entrusting this operation to a specialist workshop to avoid risk of scratching the case.

Yes, Milano Straps offers a complete collection of artisanal straps compatible with the 18mm lug width. Each strap is crafted with exceptional materials — alligator, calf, shell cordovan — and subject to rigorous quality controls. The Casati Milano service allows you to personally select the leather, follow production, and receive the product with an 18-month warranty against manufacturing defects. You can explore the collection online or book a consultation at the Milan atelier.

The lifespan of a leather strap depends on material, use and care. Quality alligator or calf, worn occasionally, can last 3-5 years. If worn daily, lifespan reduces to 2-3 years. Shell cordovan, due to its superior fibre density, tends to last longer. Excessive moisture, perspiration and prolonged sun exposure accelerate ageing. Applying a vegetable oil-based protective cream every 6-12 months extends strap life and maintains leather flexibility.