The dial design has just one objective; maximum legibility, even deep in the ocean where sunlight does not penetrate. The hour markers are large, so as to allow the maximum surface area and depth for Seiko's Lumibrite coating.

Greater security is achieved by positioning the screw-lock crown at the 4 o'clock position.

The crown has screw-down protection to prevent it from being pulled out by any accidental operation as the water resistance function is secured only when the crown is at its normal position.