Seiko "Spork" - SRP043K
...or maybe the "Sinn Seiko"?
This model did not have a long production run. Maybe there was some back channel diplomacy between Sinn and Seiko and they stopped producing it on Sinn's request? The similarities to the 857 are easy to see.
Sporting a 4R15 caliber, a mix of 7S26 and 6R15 (it has the main spring from these), it has a nice power reserve of over 50 hours.
It is a very heavy watch. Big case and a massive bracelet that it shares with the SKA series divers (lovingly known as the BFK, Big eFfing Kinetic).
The lume on the Spork is just spectacular. It charges with the slightest light and illuminates the markers for a whole night.
As you can see, mine is a bit beat up, but I love it dearly. 馃槉