Alsta Watch Nautoscaph IV Tropic AWC/AN/11/01/50. The Nautoscaph IV features a unidirectional bezel, removing the risk of it being accidentally turned while underwater, which could result in a fatal miscalculation of dive time. It is manufactured and tested to withstand the pressure of depths of 999ft (300m or 29atm). The original Nautoscaph had 999ft on its dial, a touch we loved and therefore kept. For the Nautoscaph IV, we have introduced our Valencia beads of rice bracelet to complement the piece.