Looks ARN-6 later than ARN-7. Both were NDB direction finders Tho -6 lower than -7, no reason to believe -6 came first. Like ARC-1 vs ARC-4. ARN-6 lasted all the way thru F-100 per Parsch Anyone need a as-new ARN-6 for an acft restoration? Oh yes, ARN-6 guts show Bendix MN-26 heritage as does ARN-7 Marty aka AA4RM