This compass is the same as the 103 R but has the double scale, divided into a green starboard and a red port scale, allows sailors to read the actual course on port and starboard tack from the helmsman’s normal position at the rail. You no longer have to add 45° to your reading. The green and red memory arrows tell you to tack if the figures decreases on starboard tack and to tack if the figures increase on port. The top scale allows you to read the course on downwind or to check the start line position.

See Hints & Tips Article on winning using a compass