This is an early Heathkit Marine Direction Finder model MR-21A.  Covers three bands; 188 - 410 kHz, 535 - 1620 kHz, and 1650 - 3450 kHz.  Unit is solid-state (transistors).  Operates from 6 'C' batteries at 9.0 Volts.  Has signal strength meter and sensitivity control used for direction finding.  Has 1/4 inch phone jack for headphones.

The Battery holder had been replaced as the originals become brittle and break.  Unit is fully functional, in good condition and has no other user modifications or added holes. Comes with a new 'Re-Issue' copy of the manual.  Volume control is a bit scratchy and could use some control cleaner or DeOxit.