This beauty is the Collins R-389, covering 15 Khz through 1500 Khz. The tuning is motor driven, and the receiver automatically switches RF selectivity depending on frequency. It is the VLF companion to the R-390 and is built very much like it. It is a real sweetheart to use. For some reason, the entire run of these beautiful VLF receivers, less than 1000 total, was built for the US Army, not the Navy. Strange. Here is its nomenclature plate.