This is a military (Navy?) escape compass, probably Vietnam era or later.  This is a dry card compass, with a jeweled bearing. If I flip it over, I can see that it uses two AlNiCo magnets and an induction cup. The reverse side of the compass has two small fold-out lanyard rings so that it can be worn on the wrist or tied around a leg, or hung on the neck.  The top case of the compass has a formerly luminous lubber line aligned with two small notches in the case.  Alinged with the lubber line on the top are two lines in the sides of the compass. The compass is marked on the top of the rotating card, as well as the edge, so that it can be used as a normal handheld compass, or also as a sighting compass.

Specifications:

• Manufacturer: Marine Compass Co.
• Date of Manufacture:
• Dimensions: 1 3/4” diameter, 1 1/16” high.
• Weight: 1.2 oz
• Needle: Dry card mounted on AlNiCo magnets.
• Pivot: Jeweled
• Damping: Induction
• Stop: None
• Graduations: Cardinal points with luminous lines, also marked every 30 degrees in tens of degrees (system is familiar to pilots where “30” becomes “3”, and “240” becomes “24”) with luminous tick marks, and long unnumbered tickmarks every 10 degrees, and short unnumbered tickmarks every 5 degrees.
• Marks: On bottom of base: “BUAER, U.S. NAVY”, “R18-C-1580-200” “NO.NC-1”, “MARINE COMPASS CO.”, COMPASS, MAGNETIC,”, “CARD, POCKET,”, “TYPE MC-1”, “CONTRACT”, “N3835-15495A”
• Serial Number: N/A
• Other: some corrosion on metal parts, esp. lanyard rings and underside of pivot.   There is an impact crack in the capsule visible to one side of the lubber line.