
Seiko Prospex Tuna SRPA99K1 “Green Sea Turtle”. Introduced in June 2017, this SRPA99K1 is limited to 1,881 pieces. The recommended retail price (at the time of writing) is SGD981.20 (inclusive of tax). Photo: © TANG Portfolio / TimeWerke. Elfa / Timmy.
The Seiko Prospex “Tuna” SRPA99K1, launched on 1 June 2017, is a special watch for it is a limited edition piece made for five countries/territories; namely, Hong Kong, Macau, Brunei, Malaysia and Singapore thanks to Thong Sia Watch Co., Ltd, the exclusive distributor for Seiko timepieces in this part of the world.
Limited to 1,881 pieces and water-resistant to 200 metres or 656 feet, what sets this Thong Sia exclusive Seiko Prospex Tuna SRPA99K1 apart from the rest is its green dial. It is complemented by its blue ceramic bezel.
The SRPA99K1 is powered by the Calibre 4R36 automatic movement and housed in a steel case that is further protected by a blue ceramic outer case or shroud.
The Prospex Tuna SRPA99K1 comes with a blue snake belly-style silicone accordion strap, a design that allows for the band to be expanded over a diver’s suit.

This Seiko Prospex SRPA99K1 is a limited edition piece for Hong Kong, Macau, Malaysia, Brunei and Singapore. It is an exclusive piece made for Thong Sia Watch Co., Ltd. In Singapore, it is available for sale at Seiko boutiques, City Chain stores and Seiko authorized dealers (while stocks last). Photo: © TANG Portfolio / TimeWerke. Elfa / Timmy.
Why is the Seiko Prospex Tuna SRPA99K1 dial in green?
Well, the good folks at Thong Sia adopted the colour green because they took their inspiration from the endangered green sea turtle, otherwise known by the scientific name Celonia mydas.
This watch is therefore not just known as a “Tuna” but a “Green Sea Turtle” – the Seiko Prospex Tuna SRPA99K1 “Green Sea Turtle”.
The green sea turtle is so-named not because of its “clothing” or “protective armour”; rather, it is termed “green” because of the colour of its body fat or internal fat tissue due to its diet. The green sea turtle feeds mainly on sea grass and algae.
Depending on the species and its habitat, the green sea turtle’s wide shell or carapace can be olive-green, greenish-brown, reddish-brown and even black.
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Our very first TimeWerke video, uploaded on 21 June 2017, is on a dive we took with this very Seiko Prospex Tuna SRPA99K1 “Green Sea Turtle” on a trip to Tioman in Malaysia between 15 and 18 June 2017.