2022–present · 40.5mm · caliber Seiko Cal. 6R35: in-house automatic, 21,600bph, 70h PR, 24j; hand-wind and hacking; used across modern Prospex SPB line
40.5 mm case. Wears confidently on average to larger wrists. May overhang on slender builds.
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The "Save the Ocean" caseback engraving must be present; any SPB317 without it is either a non-genuine example or a misrepresented reference.
Known issues in the market
Caseback charity text is specific to the Save the Ocean edition; standard Prospex casebacks lack this engraving.
Shallow or inconsistent engraving depth indicates an aftermarket caseback or counterfeit.
Area
What to check
What is correct
Red flag
caseback
Save the Ocean engraving
Save the Ocean text engraved with consistent depth across all characters
Absent engraving or inconsistent depth around the text; aftermarket caseback or fake
dial
Blue ocean-themed dial coloring
Blue charity edition dial with ocean coloring matching Save the Ocean product documentation
Standard Prospex blue dial without the charity edition coloring; wrong reference
Common legitimate replacements
Standard Prospex casebacks without the charity engraving are occasionally fitted; the engraving is reference-specific.
Expert resources: Seiko SPB317 product page. WatchUSeek Save the Ocean edition tracking threads.
Authentication guide
Last reviewed June 2026
The SPB317 is a 40.5mm Save the Ocean edition with a blue dial and aluminum bezel. Cal. 6R35 inside. The "Save the Ocean" branding is printed on the dial and the Seiko S medallion on the caseback incorporates a stylized ocean motif on some variants. A standard Prospex caseback substituted for the STO caseback is the primary non-obvious modification risk.
Known reproduction risks
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LOW
The SPB317 is a relatively recent reference (2022) with low reproduction market presence. The primary risk is a standard Prospex example with an STO dial fitted, claimed as original.
Caseback with a different Prospex reference number than SPB317J1
Dial without "SAVE THE OCEAN" text where it should appear
Cal. 4R36 caseback designation instead of 6R35
Dial variants by era
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Era
Description
Identifiers
2022 to present
Blue sunburst dial with applied indices, "SAVE THE OCEAN" text, and "DIVER'S 200M" designation. The 40.5mm case is more compact than the older Turtle or Sumo.
Blue sunburst dial
"SAVE THE OCEAN" text printed on the dial at 6 o'clock
"PROSPEX" and "DIVER'S 200M" designation
Date window at 3
Unidirectional aluminum bezel
Crown at 4 o'clock
Sapphire crystal
Service part flags
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Dial
Original: Blue sunburst with "SAVE THE OCEAN" text. The text is small but crisp on originals; blurred or offset text indicates a non-original dial.
Replacement tells
Missing "SAVE THE OCEAN" text on the dial
Standard Prospex dial without the STO designation substituted
Text with blurred or uneven edges
Bezel
Original: Unidirectional aluminum insert with 120-click action.
Replacement tells
Bidirectional rotation
Ceramic insert in place of aluminum
Crown
Original: Non-screw-down crown at 4 o'clock.
Replacement tells
Crown repositioned to 3 o'clock
Caseback
Original: Solid caseback with SPB317J1 reference number, Seiko S medallion, and Cal. 6R35 designation.
Replacement tells
Generic Prospex caseback without the SPB317J1 reference number
Cal. 4R36 designation indicating a lower-tier movement swap
Case back markings
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2022 to present
SPB317J1 reference number
"DIVER'S 200M" designation
Seiko S medallion
Cal. 6R35 designation
Serial number in Seiko standard format
Movement tells
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Cal. 6R35 at 28,800 bph; 70-hour power reserve. Hackable and manually windable.
Any SPB317 with a 4R36 movement (21,600 bph, 6 ticks per second) has had the movement downgraded.
The caseback is solid; a display caseback is non-original.
Sources: Seiko Prospex SPB317 product page; Fratello -- SPB317 review.
