Introduction
The Seiko Prospex SPB151, affectionately known as the 'Willard' reissue, is a watch that needs no introduction among dive watch enthusiasts. It resurrects the iconic 6105-8110 from the 1970s—a watch immortalized by Martin Sheen in Apocalypse Now and revered for its asymmetrical case, cushion shape, and rugged dependability. Seiko’s modern interpretation, launched in 2020 as part of the Prospex line, updates the original with a sapphire crystal, a 200-meter water resistance rating, and the reliable 6R35 automatic movement.
For the young collector seeking a piece of horological history without the fragility of a vintage piece, the SPB151 offers a compelling proposition. It retains the distinctive 'tortoise' case profile—wide, flat, and angular—while improving legibility, accuracy, and serviceability. This review dissects every aspect of the watch, from its movement architecture to its wrist presence, to help you decide if this modern classic deserves a spot in your collection.
Manufacture History
Seiko began as a watch and clock shop in Tokyo in 1881 and grew into one of the world’s most respected watch manufacturers. The brand’s dive watch heritage started in 1965 with the 62MAS, but the 1970s 6105 'Willard' became a cultural icon thanks to its use in the Vietnam War and Hollywood. The SPB151 is a faithful reissue of that legendary model, blending vintage aesthetics with modern Seiko engineering.
Movement
At the heart of the SPB151 beats the Seiko caliber 6R35, an automatic movement with 24 jewels, a frequency of 21,600 vibrations per hour, and a substantial 70-hour power reserve. This movement is an evolution of the 6R15, offering a longer power reserve and improved accuracy. It features Diashock shock protection and a stop-seconds function for precise time-setting. While the finishing is utilitarian—perlage on the rotor and minimal decoration—the 6R35 is a reliable workhorse that prioritizes function over form. It is not COSC-certified, but Seiko’s in-house manufacturing ensures consistent quality.
Specifications
- Case Diameter: 42.7mm
- Case Thickness: 13.2mm
- Lug-to-Lug: 48.5mm
- Case Material: Stainless steel
- Crystal: Sapphire with anti-reflective coating
- Water Resistance: 200 meters
- Lume: Seiko LumiBrite
- Strap: Silicone rubber with pin buckle
Wrist Feel
On the wrist, the SPB151 wears surprisingly compact for its 42.7mm diameter. The short 48.5mm lug-to-lug and the downward-curving lugs allow it to sit flat on wrists as small as 6.5 inches. The silicone strap is soft and pliable, though it can attract lint; many owners swap it for a NATO or tropic strap. At 13.2mm thick, it’s not a slim watch, but the cushion case distributes the weight evenly, making it comfortable for all-day wear.
The crown at 4 o’clock—a signature of the original—keeps it from digging into the wrist, and the signed screw-down crown operates smoothly. The watch feels solid and purposeful, with a reassuring heft that speaks to its dive tool heritage. It’s a watch you forget you’re wearing until you catch a glimpse of that iconic case shape.
Accuracy
In real-world use, the 6R35 typically runs within +10 to +20 seconds per day out of the box, though regulation can improve it to +5 to +10. Seiko’s official tolerance is -15 to +25 seconds per day. With consistent wear, expect around +12 s/d. The 70-hour power reserve is a genuine advantage for weekend rotation, maintaining accuracy through Monday morning.
Occasions
The SPB151 is a versatile tool watch suited for sport, daily wear, and travel. Its 200m water resistance and robust construction make it ideal for swimming, snorkeling, and casual adventures. The vintage-inspired design also pairs well with jeans and a t-shirt, though it may feel out of place in formal settings.
Wrist Presence
4/5 — The Willard’s asymmetrical case and broad bezel command attention without being ostentatious. It’s a conversation starter for those in the know, yet understated enough for casual wear.
Reference Variants
The SPB151 is part of a family of Willard reissues. The SPB153 offers a steel bracelet, the SPB155 a green dial, and the SPB239 a more vintage-correct dial with gilt accents. Each variant retains the same case and movement, differing only in dial color and strap/bracelet options.
Family References
Other notable Seiko Prospex divers include the SPB143 (62MAS reissue), SPB185 (MM200), and SPB187 (MM300). These share the same 6R35 movement and similar build quality, offering different case shapes and heritage.
Other by Brand
Seiko’s catalog is vast. The Presage line offers dress watches, the 5 Sports line provides affordable automatics, and Grand Seiko represents the pinnacle of Japanese watchmaking. For dive watch enthusiasts, the Prospex line is the go-to.
Similar Watches
Competitors in the vintage-inspired dive watch segment include the Tudor Black Bay 58 (39mm, in-house movement), the Longines Legend Diver (super-compressor style), and the Oris Divers Sixty-Five (slim profile, domed crystal). Each offers a different take on mid-century diving heritage.
Homages
For budget-conscious collectors, the Steeldive SD1970 ($120) and Addiesdive Willard ($80) offer direct homages to the 6105 case shape with NH35 or quartz movements. While lacking the finishing and brand heritage, they provide the look at a fraction of the cost.
Investment Value
The SPB151 has an MSRP of $1,200 and currently retails around $1,300. Pre-owned examples range from $800 to $1,100. The market is stable, with no significant appreciation expected. This is a watch to buy for enjoyment, not speculation. No major auction history exists.
Service Interval
Seiko recommends service every 5 years. A full service at an authorized center costs approximately $250, though independent watchmakers can often do it for less. The 6R35 is a robust movement with readily available parts.
Pros and Cons
Pros: Iconic Willard case design, sapphire crystal, 200m water resistance, 70-hour power reserve, excellent LumiBrite lume.
Cons: Silicone strap attracts lint, crown at 4 o’clock may feel awkward, movement accuracy can be inconsistent, no quick-adjust clasp on bracelet variants.
Final Verdict
The Seiko Prospex SPB151 is a masterful reissue that honors the 6105 Willard while delivering modern reliability. Its distinctive case, superb lume, and robust 6R35 movement make it a daily-wearable dive watch with genuine character. For the young collector seeking a piece of horological history without vintage headaches, this is one of the best values in the Prospex lineup.
