Strap for Valiant Auto 40 Stainless Steel / Black

The lug width of the Hamilton Valiant H39515733 is 20 millimetres. This measurement is determined by the distance between the two inner lugs of the case that accommodate the spring bar. To verify it, use a digital calliper and measure the space between the lugs: the result must be 20.00mm ± 0.1mm. An incorrect measurement will result in purchasing incompatible straps.

There is no single 'best' strap in absolute terms, as the choice depends on usage and personal aesthetic preference. For formal wear, an alligator leather strap in black with vegetable tanning is ideal and develops a fascinating patina over time. For those who wish to emphasise the sports character, a NATO strap in nylon cordura in navy blue or military green enhances the tachymetre bezel. If engaging in sports, a black FKM rubber strap guarantees maximum durability. Cognac calf leather creates the best aesthetic balance between the coldness of steel and the warmth of leather.

Changing the strap requires the use of a spring bar tool (a dual-pronged steel device). Position the tool under one of the lateral pins and apply gentle upward pressure, leveraging the internal spring of the pin. Once the first pin is released, repeat the procedure from the opposite side and extract the old strap. Insert the pins of the new strap into the lugs, ensuring the inner shoulder of the strap is perfectly aligned with the lug shoulder of the case. Press downward until the pin engages the spring, creating a 'click' of security. Repeat from the other side. Always verify proper engagement before wearing the watch.

Yes, because the lug width is a standard 20mm, any strap designed for this measurement from a quality maker is compatible. However, not all aftermarket products adhere to precise tolerances: some have shoulders slightly wider or narrower, creating excessive friction or dangerous play. Artisanal and specialist brand straps guarantee tolerances of ±0.05mm, whilst mass-produced economy straps often have tolerances of ±0.5mm, risking lug damage. It is essential to verify technical specifications before purchase and to choose suppliers who certify manufacturing dimensions.

A high-quality leather strap—vegetable tanned and handcrafted—lasts on average 3-4 years with daily wear. Lifespan depends on factors such as direct sunlight exposure, ambient humidity, perspiration, cleaning frequency and type of tanning. Vegetable-tanned straps age better than chrome-tanned ones, developing a more coherent patina. The area of attachment to the buckle, exposed to constant bending, is the most likely failure point. Periodic maintenance—cleaning with a damp cloth and six-monthly leather balm treatment—extends lifespan. Rubber or NATO straps have virtually unlimited durability, exceeding 10 years, provided they are not exposed to extreme heat.