Best Watch Straps for the Seiko Prospex SPB143 and 1959 Alpinist

In 1959, Seiko introduced a watch that did not fit into any existing category. Designed for mountaineering — for the serious alpinist who needed a precise, reliable instrument on Japanese mountain peaks — it featured a graduated dial, a compass bezel, and mountain-shaped hour markers at 12, 6, and 9 o'clock. It was the first Seiko sport watch and the founding reference of the entire Alpinist tradition.

Six years later, in 1965, Seiko introduced its first dedicated professional diving watch — the 62MAS, named for the movement calibre it housed. Rated to 150m and carried on the Japanese Antarctic Research Expedition (JARE) as standard equipment, the 62MAS established Seiko's credibility in professional dive watch production. Its design was deliberately clean and readable — a conventional dive watch executed with the same attention to operational legibility that Seiko brought to all its professional instrument watches.

Both watches were reissued as modern Prospex references in the 2019-2022 period. Both are worth wearing straps that honour their specific heritages rather than treating them as generic Seiko Prospex dive watches.

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Strap Sizes — SPB143 62MAS and 1959 Alpinist Family

Seiko Prospex SPB143 / SBDC101 "62MAS" (2019-current): 20mm lugs. 40.5mm case diameter, 13.2mm thick, 47.6mm lug-to-lug. Drilled lug holes for easy strap changing.

Seiko Prospex SPB155 / SPB157 1959 Alpinist (2019-current): 20mm lugs. 38mm case diameter, 12.9mm thick. Green dial (SPB155), brown dial (SPB157).

Seiko Prospex SPB249 / SPB251 1959 Alpinist Modern Interpretation (2022-current): Lug width is disputed — some sources list 19mm, others list 20mm. Measure the gap between your lugs directly before ordering.

Quick reference:

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The Two Heritage Stories — Two Different Strap Logics

The SPB143 62MAS and the 1959 Alpinist share the Prospex family name but draw from completely different operational worlds.

The 62MAS is a professional diving watch. Its 1965 original was worn on the Japanese Antarctic Research Expedition and carried on professional dives. The correct straps reference this operational dive world — tropical rubber, operational nylon, padded leather.

The 1959 Alpinist is a mountaineering watch. The correct straps reference the alpine world — canvas that references mountain equipment, robust leather in earthy tones, olive nylon. The green graduated dial of the SPB155 specifically demands earthy, mountain-palette straps rather than the maritime palettes that suit the 62MAS.

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Best Rubber Straps for the SPB143 62MAS

Tropical style FKM in black at 20mm — the most historically resonant 62MAS combination. The vintage basket-weave and honeycomb surface patterns reference the 1960s Japanese professional dive watch rubber era directly — the same era when the original 62MAS was being worn on the JARE expedition.

Brown tropical FKM at 20mm — for the most aged vintage character. Particularly effective on the 62MAS's green lume indices.

Classic FKM rubber in black at 20mm — the most practical active choice for the 62MAS's 200m water resistance.

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Best Rubber Straps for the 1959 Alpinist

Classic FKM rubber in black at 20mm — practical active choice for the Alpinist's 200m rating in mountain weather conditions.

Green FKM rubber at 20mm — for the SPB155 green dial specifically. Creates a fully mountain-palette combination.

Grey FKM rubber at 20mm — for the blue dial SPB249 in active contexts.

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Best Nylon Straps for the SPB143 62MAS

Single-pass nylon — Original at 20mm. Most appropriate 62MAS colourways:

• Black — the most operational and most purposeful.
• Navy — for the blue lume variant. Creates maritime coherence with the blue-toned indices.
• Olive / khaki — for the most vintage Japanese diving expedition aesthetic.
• Black and grey — the most collector-oriented combination.

Marine Nationale elastic at 20mm — the most comfortable 62MAS daily wear option. Navy or black.

RAF single-pass nylon at 20mm — for the most specifically military-expedition aesthetic. The JARE Antarctic expedition heritage connects the 62MAS to the world of operational expedition equipment that the RAF strap references.

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Best Nylon and Canvas Straps for the 1959 Alpinist

Canvas at 20mm in olive or khaki — the most specifically appropriate strap for the 1959 Alpinist. The original 1959 sport watch was designed for Japanese mountain climbers using equipment made from canvas — rope bags, equipment sacks, rucksacks. Olive canvas on the green dial SPB155 creates a fully mountain-palette combination where every element references the same alpine world.

Single-pass nylon — Original at 20mm. Most appropriate Alpinist colourways:

• Olive / khaki — the most mountain-appropriate nylon combination for both green and blue dial variants.
• Green accent — for the SPB155 green dial, echoing the graduated dial colour.
• Brown and tan stripe — for the SPB157 brown dial.
• Black — the most minimal combination.

Paratrooper elastic at 20mm — the most comfortable daily wear option for active mountain use.

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Best Leather Straps for the SPB143 62MAS

Brown vintage two-stitch calfskin at 20mm — the most characterful 62MAS leather combination. The warm brown two-stitch references the 1965 era of the original 62MAS. On the green lume dial, the warm brown creates a temperature contrast that reads as specifically vintage.

Dark brown padded calfskin at 20mm — the most substantial everyday leather. The padded construction suits the 62MAS's 13.2mm case thickness proportionally.

Classic black calfskin at 20mm — the most formal 62MAS combination.

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Best Leather Straps for the 1959 Alpinist

Brown vintage two-stitch calfskin at 20mm — the most period-correct Alpinist leather. The warm brown references the 1959 era of the original mountain watch and the leather equipment of Japanese alpinists of that decade. On the green dial SPB155, warm brown creates an earthy, mountain-coherent combination.

Dark brown suede at 20mm — the most specifically alpine-appropriate leather. Suede references the warm, matte, tactile quality of mountain equipment leather.

Tan suede at 20mm — particularly effective on the SPB157 brown dial.

Olive suede at 20mm — for the SPB155 green dial. Creates a fully mountain-palette tonal combination.

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The Seiko Prospex Cluster

CNS covers the primary Seiko Prospex references:

Seiko 5 Sports SRPD — 22mm. The entry diver with multiple dial variants.

Seiko Alpinist — 20mm. The modern Alpinist.

Seiko Captain Willard — 20mm. The 6105-8110 asymmetric crown guard.

Seiko Prospex SPB143 / 1959 Alpinist — 20mm. The 62MAS and vintage Alpinist reissue family.

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Recommended Combinations

SPB143 62MAS — most historically resonant — black tropical FKM at 20mm — 1965 Japanese dive expedition era rubber.

SPB143 62MAS — most characterful dress-sport — brown vintage two-stitch leather at 20mm.

SPB155 Alpinist green dial — most mountain-coherent — olive canvas at 20mm.

SPB155 Alpinist green dial — most relaxed leather — olive suede at 20mm.

SPB157 Alpinist brown dial — most period-correct — brown vintage two-stitch leather at 20mm.

SPB249 / SPB251 — measure first — olive canvas or brown vintage two-stitch at whichever of 19mm or 20mm fits your specific watch.

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Frequently Asked Questions

What size strap does the Seiko SPB143 62MAS take? 20mm — confirmed by multiple independent sources. The 40.5mm case uses 20mm lugs with drilled through-holes for easy strap changing.

What size strap does the 1959 Alpinist SPB155 take? 20mm for the SPB155 and SPB157. The SPB249 and SPB251 Modern Interpretation variants use either 19mm or 20mm depending on the specific reference — measure directly before ordering.

What is the best strap for the SPB155 green dial Alpinist? Olive canvas at 20mm for the most mountain-coherent combination — the green canvas and the green graduated dial create a fully alpine-palette combination. Olive suede for the most relaxed leather alternative. Brown vintage two-stitch leather for the warm period-correct contrast.

What is the best strap for the SPB143 62MAS? Black tropical style FKM at 20mm for the most period-correct active combination — the vintage rubber texture references the 1965 JARE expedition era directly. Brown vintage two-stitch leather for the most characterful dress-sport transformation.

What was the Japanese Antarctic Research Expedition (JARE) connection to the 62MAS? Seiko's 62MAS was carried as standard equipment on the Japanese Antarctic Research Expedition, establishing it as a professional instrument watch in the same category as the Rolex Submariner and Omega Seamaster 300 of the same era. The JARE connection is the 62MAS's most important operational credential and the reason the SPB143 reissue is treated as a serious heritage piece rather than a budget diver.

All CNS straps for the Seiko SPB143 62MAS and 1959 Alpinist are available at 19mm and 20mm. Standard delivery worldwide. 30-day returns.