The Analog benefits from a super durable, tarnish-free coating meaning you never need to polish it. Overall case diameter 15cm, depth 4cm. The instrument features a good quality quartz movement and black Arabic numerals upon a crisp white face. The additional (red) hand gives an at-a-glance guide to the tidal state, once set to your location. Uses 1xAA battery. TARNISH-FREE - Tarnish-free instruments have been coated with a newly developed protective coating using advanced surface treatment technology. Far superior to lacquers and varnishes, it can withstand more than 720 hours (the longest test period for this process) under NSS (Neutral Sea Salt) laboratory testing. NSS testing is a certificated and standardised test method used to check corrosion resistance of coatings on metals such as brass, zinc and steel. This means your instruments will stay looking good for longer even when exposed to the harsh marine environment for extended periods. TIDE CLOCKS - Tide clocks provide an at-a-glance indication by means of an additional hand that takes approximately 12 hours and 25 minutes to go 'round the clock'. Because the lunar cycle varies in length day by day but is constant over a cycle of 28 days, there will be times when the tide indicator varies by a few minutes ahead of or behind the actual tides.