75mm diameter; mica card; graduated 0-360 degrees in 5 degree sections plus cardinal points. 2 x Alnico magnets rigidly attached to card float; Cap of artificial sapphire, Pivot top of platinum iridium alloy
Lighting
Electric lighting from below; 3V from dry cell batteries
Grid Ring
Has 0 - 360 degree graduation. Easy Course Determination by moving knob fixed on grid plate. Easy reading; Plastic T-Shaped grid