This clever 1" diameter compass mounts to the proximal square portion of SCUBAPRO consoles.
The C-1 compass is a compact, fast response top-reading compass. The magnetic field sensitive portion of the compass is built into the needle, and the reduced size and weight of the needle and responsible for a very fast response.
The course-setting bezel is used to give the top-reading line reference. The four cardinal points are indicated on the bezel, but due to the reduced size, numerals in between have been replaced with dots every 30 degrees.
To allow the largest possible digits on the face plate, the ending zero has been removed from the numerals on the plate itself. Therefore the numeral 3 represents 30 degrees, 27 represents 270 degrees, and so on.
Using the compass: Align yourself with your reference point, then align the bezel with the needle and read the numerals corresponding to the direction of your reference point. While swimming in the direction indicated by the numerals, keep the bezel aligned with the needle.