Seiko SNM017K1 Samurai "The Ninja" - Limited Edition 021/500 (2006)
There is also a limited black dialed series SNM015K1 of 500 pieces

The Ninja shares the same Diver's Extension and clasp
with the Yellow Monster. Here it is shown opened. Very practical not only for divers, but also for people living in hot climate zones to open the extension and let the skin under the bracelet breath and dry for a while.