Channel Range Polished Chrome Tide ClockBrass Made of solid unlacquered brass and bevelled glass. Chrome Made by anodising chrome onto brass instruments, not steel. Clocks have a quartz movement and the barometers have a sealed unit with an adjustment mechanism. Tide clocks feature an additional hand which records lunar time over a 24 hour and 50 minute period which approximates to the cycle of high and low tides. Channel range dimensions : Back diameter 117mm Glass diameter 84mm Depth 52mm