Seamaster aqua terra 150 m omega master co axial 385 mm steel on steel features anti magnetic chronometer date screw in crown transparent case back crystal domed scratch resistant sapphire crystal with anti reflective treatment on both sides case steel dial blue water resistance 150mmovement caliber omega 8500 self winding movement with co axial escapement for greater precision stability and durability resistant to magnetic fields greater than 15 000 gauss free sprung balance with sili