All Seiko lines › Prospex › Sea
“Marinemaster 300”
Seiko Prospex Sea, 44.3 mm (8L35)
Collector nickname. Where the name comes from
5 versions of this watch are on Seiko's own sites right now, across 8 regions. Last checked Nov 13, 2026.
Estimated US price: About $3,100 to $3,845 from Seiko's US list price and its list prices in other countries, converted.
Retailers ask: no retailer listing matched yet.
Photos are Seiko's own, shown from Seiko's sites. Click a photo to jump to that version.
- Calibre
- 8L35
- Case diameter
- 44.3 mm
- Thickness
- 15.4 mm
- Lug to lug
- 50.5 mm
- Variants listed now
- 5
- Regions
- 8
Listed means the watch was on an official Seiko regional site or store at the last check. It does not mean it is in stock, and it does not tell us whether Seiko is still making it.
Versions listed now
Same case and movement in every row. What changes is the colour, the strap or bracelet, the finish and where Seiko sells it. Seiko's spec sheets don't state dial colour, so a colour appears only where Seiko's US store tags one.
| Photo | Reference | Colour | Strap / bracelet | Case | Edition | Listed in | Seiko list price | Buy | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 | SLA035 Also coded SLA035J1 | Not published | Silicone | Stainless steel (hard coating)with ceramic bezel | The Black Series Limited Edition | 4 regions Indonesia, Malaysia, Singapore, UK | 14,400 MYR Malaysia · Nov 13, 2026 about $3,845 in US dollars | No seller matched yet | ||||||||
Where Seiko lists it (4 sites) and its list pricesBuying options (0)No seller offer has been matched to this exact variant yet. | ||||||||||||||||
 | SLA021 Also coded SLA021J1 | Not published | Not stated 222 g | Stainless steel (super hard coating) with stainless steel bezel | Regular | 3 regions Australia, Hungary, USA | 3,100 USD USA · Nov 13, 2026 | No seller matched yet | ||||||||
Where Seiko lists it (3 sites) and its list pricesBuying options (0)No seller offer has been matched to this exact variant yet. | ||||||||||||||||
 | SLA023 Also coded SLA023J1 | Not published | Not stated Clasp: Three-fold clasp with secure lock & push button release, solid & slide adjuster 222 g | Stainless steel with ceramic bezel | 1968 Heritage Diver's Watch | 3 regions Australia, Hungary, USA | 3,100 USD USA · Nov 13, 2026 | No seller matched yet | ||||||||
Where Seiko lists it (3 sites) and its list pricesBuying options (0)No seller offer has been matched to this exact variant yet. | ||||||||||||||||
 | SLA019 Also coded SLA019J1 | Not published | Not stated | Baja tahan karat (lapisan super keras) dengan bingkai cincin baja tahan karat Seiko's regional wording | Seiko Prospex The 1968 Automatic Diver’s Commemorative Limited Edition | 2 regions Indonesia, Portugal | 3,400 EUR Portugal · Nov 13, 2026 about $3,765 in US dollars | No seller matched yet | ||||||||
Where Seiko lists it (2 sites) and its list pricesBuying options (0)No seller offer has been matched to this exact variant yet. | ||||||||||||||||
 | SLA047 Also coded SLA047J1 | Not published | Not stated Clasp: Three-fold clasp with secure lock & push button release, solid & slide adjuster 222 g | Stainless steel with ceramic bezel | Seiko 140th Anniversary Limited Edition | 1 region USA | 3,200 USD USA · Nov 13, 2026 | No seller matched yet | ||||||||
Where Seiko lists it (1 site) and its list prices
Buying options (0)No seller offer has been matched to this exact variant yet. | ||||||||||||||||
Where to buy
No retailer listing has been matched to a version on this line yet.
Estimated US prices use Seiko's US list price where there is one. Otherwise they are the middle of Seiko's list prices in other countries, converted at rates dated Nov 12, 2026 from ExchangeRate-API (free open endpoint). Those list prices include each country's sales tax, so a converted figure usually runs higher than a US price would. Retailer prices are asking prices on the date shown, not sold prices, and leave out shipping, tax and import charges.
The build
| Movement | Automatic with manual winding | Seiko product page |
|---|---|---|
| Functions | 28,800 vibrations per hour (8 beats per second) Stop second hand function Date display | Seiko product page |
| Power reserve / battery | Approx. 50 hours | Seiko product page |
| Water resistance | 300m / 1000ft for saturation diving | Seiko product page |
| Crystal | Sapphire crystal | Seiko product page |
| Lug width | 20 mm | Seiko product page |
| Seiko case codes | 8L35-00S0, 8L35-00Y0, 8L35-01E0, 8L35-01F0 | Seiko catalog data |
Why these share a page
Every version here is published by Seiko with calibre 8L35 and either the same Seiko case code or the same case size. 10 reference codes lead to this page.
Seiko publishes no lug-to-lug for these versions: SLA019. They are on this page because the calibre, diameter and thickness match.
What people call it
A name is shown only where a source ties it to a reference on this page. Collector nicknames are not Seiko's names unless the row says so.
| “Marinemaster 300” | Collector nickname. Source names SLA021J1. “Without creating any noise about it, Seiko sneaked in a new version of the Marinemaster: the Prospex Marinemaster 300 SLA021J1.” | Fratello read 2026-11-12 |
|---|
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